to find phone number Look for a phone number in a string
For underline android: how to add Underline in the String
for dailer 
add in menifest 
<uses-permission android:name="android.permission.CALL_PHONE" />
for call button 
Button callButton = (Button)findViewById(R.id.btnCall);
txtPhn = (EditText)findViewById(R.id.txtPhnNumber);
callButton.setOnClickListener(new OnClickListener() {
    public void onClick(View v) {
        try {
                Intent callIntent = new Intent(Intent.ACTION_CALL);
                callIntent.setData(Uri.parse("tel:"+txtPhn.getText().toString()));
                startActivity(callIntent);
            } catch (ActivityNotFoundException activityException) {
                Log.e("Calling a Phone Number", "Call failed", activityException);
            }
    }
});
try this
 <Button
android:id="@+id/btnview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@null"
 />
in class 
Button btn = (button)findViewbyid(R.id.btnview);
btn.setText("YOUR Phone number");
btn.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
 Intent callIntent = new Intent(Intent.ACTION_CALL);
                callIntent.setData(Uri.parse("tel:"+btn.getText().toString()));
                startActivity(callIntent);
            } catch (ActivityNotFoundException activityException) {
                Log.e("Calling a Phone Number", "Call failed", activityException);
            }
                }
            });