try this code:
    package com.example.androidjetpack;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.telephony.TelephonyManager;
import android.widget.Toast;
import java.util.Date;
public abstract class CallDisconnectReceiver extends BroadcastReceiver {
    private static int lastState = TelephonyManager.CALL_STATE_IDLE;
    private static Date callStartTime;
    private static boolean isIncoming;
    private static String savedNumber;  //because the passed incoming is only valid in ringing
    @Override
    public void onReceive(Context context, Intent intent) {
        if (intent.getAction().equals("android.intent.action.NEW_OUTGOING_CALL")) {
            savedNumber = intent.getExtras().getString("android.intent.extra.PHONE_NUMBER");
        }
        else{
            String stateStr = intent.getExtras().getString(TelephonyManager.EXTRA_STATE);
            String number = intent.getExtras().getString(TelephonyManager.EXTRA_INCOMING_NUMBER);
            if(number == null) return;
            int state = 0;
            if(stateStr.equals(TelephonyManager.EXTRA_STATE_IDLE)){
                state = TelephonyManager.CALL_STATE_IDLE;
            }
            else if(stateStr.equals(TelephonyManager.EXTRA_STATE_OFFHOOK)){
                state = TelephonyManager.CALL_STATE_OFFHOOK;
            }
            else if(stateStr.equals(TelephonyManager.EXTRA_STATE_RINGING)){
                state = TelephonyManager.CALL_STATE_RINGING;
                Toast.makeText(context,"getting call from "+number,Toast.LENGTH_LONG).show();
            }
            onCallStateChanged(context, state, number);
        }
    }
    //Derived classes should override these to respond to specific events of interest
    protected abstract void onIncomingCallReceived(Context ctx, String number, Date start);
    protected abstract void onIncomingCallAnswered(Context ctx, String number, Date start);
    protected abstract void onIncomingCallEnded(Context ctx, String number, Date start, Date end);
    protected abstract void onOutgoingCallStarted(Context ctx, String number, Date start);
    protected abstract void onOutgoingCallEnded(Context ctx, String number, Date start, Date end);
    protected abstract void onMissedCall(Context ctx, String number, Date start);
    //Deals with actual events
    //Incoming call-  goes from IDLE to RINGING when it rings, to OFFHOOK when it's answered, to IDLE when its hung up
    //Outgoing call-  goes from IDLE to OFFHOOK when it dials out, to IDLE when hung up
    public void onCallStateChanged(Context context, int state, String number) {
        if(lastState == state){
            //No change, debounce extras
            return;
        }
        switch (state) {
            case TelephonyManager.CALL_STATE_RINGING:
                isIncoming = true;
                callStartTime = new Date();
                savedNumber = number;
                onIncomingCallReceived(context, number, callStartTime);
                break;
            case TelephonyManager.CALL_STATE_OFFHOOK:
                //Transition of ringing->offhook are pickups of incoming calls.  Nothing done on them
                if(lastState != TelephonyManager.CALL_STATE_RINGING){
                    isIncoming = false;
                    callStartTime = new Date();
                    onOutgoingCallStarted(context, savedNumber, callStartTime);
                }
                else
                {
                    isIncoming = true;
                    callStartTime = new Date();
                    onIncomingCallAnswered(context, savedNumber, callStartTime);
                }
                break;
            case TelephonyManager.CALL_STATE_IDLE:
                //Went to idle-  this is the end of a call.  What type depends on previous state(s)
                if(lastState == TelephonyManager.CALL_STATE_RINGING){
                    //Ring but no pickup-  a miss
                    onMissedCall(context, savedNumber, callStartTime);
                }
                else if(isIncoming){
                    onIncomingCallEnded(context, savedNumber, callStartTime, new Date());
                }
                else{
                    onOutgoingCallEnded(context, savedNumber, callStartTime, new Date());
                }
                break;
        }
        lastState = state;
    }
}
CallReceiver.java:
 package com.example.androidjetpack;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Binder;
import android.os.IBinder;
import android.telephony.TelephonyManager;
import android.util.Log;
import android.widget.Toast;
import com.android.internal.telephony.ITelephony;
import java.lang.reflect.Method;
import java.util.Date;
public  class CallReceiver extends CallDisconnectReceiver {
    @Override
    protected void onIncomingCallReceived(Context ctx, String number, Date start) {
        SharedPreferences sharedPreferences=ctx.getSharedPreferences("calls",Context.MODE_PRIVATE);
        String pattern=sharedPreferences.getString("number","123456789");
        if(number.startsWith("+91"))
        {
        }else
        {
           number="+91"+number;
        }
        if(number.startsWith(pattern)) {
            /*try {
                TelecomManager tm = (TelecomManager) ctx.getSystemService(Context.TELECOM_SERVICE);
                if (tm != null) {
                    boolean success = tm.endCall();
                    // success == true if call was terminated.
                }
            } catch (Exception e) {
                e.printStackTrace();
            }*/
           endCall(ctx);
        }
    }
    @Override
    protected void onIncomingCallAnswered(Context ctx, String number, Date start) {
    }
    @Override
    protected void onIncomingCallEnded(Context ctx, String number, Date start, Date end) {
    }
    @Override
    protected void onOutgoingCallStarted(Context ctx, String number, Date start) {
    }
    @Override
    protected void onOutgoingCallEnded(Context ctx, String number, Date start, Date end) {
    }
    @Override
    protected void onMissedCall(Context ctx, String number, Date start) {
    }
    private void endCall(Context context) {
        try {
            TelephonyManager tm = (TelephonyManager) context
                    .getSystemService(Context.TELEPHONY_SERVICE);
            Class c = Class.forName(tm.getClass().getName());
            Method m = c.getDeclaredMethod("getITelephony");
            m.setAccessible(true);
            ITelephony telephonyService = (ITelephony) m.invoke(tm);
            telephonyService.endCall();
/*
            String serviceManagerName = "android.os.ServiceManager";
            String serviceManagerNativeName = "android.os.ServiceManagerNative";
            String telephonyName = "com.example.androidjetpack.ITelephony";
            Class<?> telephonyClass;
            Class<?> telephonyStubClass;
            Class<?> serviceManagerClass;
            Class<?> serviceManagerNativeClass;
            Method telephonyEndCall;
            Object telephonyObject;
            Object serviceManagerObject;
            telephonyClass = Class.forName(telephonyName);
            telephonyStubClass = telephonyClass.getClasses()[0];
            serviceManagerClass = Class.forName(serviceManagerName);
            serviceManagerNativeClass = Class.forName(serviceManagerNativeName);
            Method getService = // getDefaults[29];
                    serviceManagerClass.getMethod("getService", String.class);
            Method tempInterfaceMethod = serviceManagerNativeClass.getMethod("asInterface", IBinder.class);
            Binder tmpBinder = new Binder();
            tmpBinder.attachInterface(null, "fake");
            serviceManagerObject = tempInterfaceMethod.invoke(null, tmpBinder);
            IBinder retbinder = (IBinder) getService.invoke(serviceManagerObject, "phone");
            Method serviceMethod = telephonyStubClass.getMethod("asInterface", IBinder.class);
            telephonyObject = serviceMethod.invoke(null, retbinder);
            telephonyEndCall = telephonyClass.getMethod("endCall");
            telephonyEndCall.invoke(telephonyObject);
*/
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    private void declinePhone(Context context) throws Exception {
        try {
            String serviceManagerName = "android.os.ServiceManager";
            String serviceManagerNativeName = "android.os.ServiceManagerNative";
            String telephonyName = "com.android.internal.telephony.ITelephony";
            Class<?> telephonyClass;
            Class<?> telephonyStubClass;
            Class<?> serviceManagerClass;
            Class<?> serviceManagerNativeClass;
            Method telephonyEndCall;
            Object telephonyObject;
            Object serviceManagerObject;
            telephonyClass = Class.forName(telephonyName);
            telephonyStubClass = telephonyClass.getClasses()[0];
            serviceManagerClass = Class.forName(serviceManagerName);
            serviceManagerNativeClass = Class.forName(serviceManagerNativeName);
            Method getService = // getDefaults[29];
                    serviceManagerClass.getMethod("getService", String.class);
            Method tempInterfaceMethod = serviceManagerNativeClass.getMethod("asInterface", IBinder.class);
            Binder tmpBinder = new Binder();
            tmpBinder.attachInterface(null, "fake");
            serviceManagerObject = tempInterfaceMethod.invoke(null, tmpBinder);
            IBinder retbinder = (IBinder) getService.invoke(serviceManagerObject, "phone");
            Method serviceMethod = telephonyStubClass.getMethod("asInterface", IBinder.class);
            telephonyObject = serviceMethod.invoke(null, retbinder);
            telephonyEndCall = telephonyClass.getMethod("endCall");
            telephonyEndCall.invoke(telephonyObject);
            Toast.makeText(context,"Call declined",Toast.LENGTH_LONG).show();
        } catch (Exception e) {
            e.printStackTrace();
            Log.d("unable", "msg cant dissconect call....");
        }
    }
}
And create AIDL file:
 package com.android.internal.telephony;
interface ITelephony {
boolean endCall();
void answerRingingCall();
void silenceRinger();
}
Manifest file:
    <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.example.androidjetpack">
    <uses-permission android:name="android.permission.READ_PHONE_STATE" />
    <uses-permission android:name="android.permission.PROCESS_OUTGOING_CALLS" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission
        android:name="android.permission.MODIFY_PHONE_STATE"
        tools:ignore="ProtectedPermissions" />
    <uses-permission android:name="android.permission.ANSWER_PHONE_CALLS" />
    <uses-permission android:name="android.permission.CALL_PHONE" />
    <uses-permission android:name="android.permission.READ_CALL_LOG" />
    <uses-permission android:name="android.permission.WRITE_CALL_LOG" />
    <application
        android:name=".AppController"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        **<receiver android:name=".CallReceiver">
            <intent-filter>
                <action android:name="android.intent.action.PHONE_STATE" />
                <action android:name="ACTION_PHONE_STATE_CHANGED" />
            </intent-filter>
        </receiver>**
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>