I've tried making a retrofit call to an API endpoint, but it's returning a 400 error, however my curl request is working perfectly fine. I can't seem to spot the error, could someone double check my work to see where I made a mistake?
The curl call that works:
curl --request POST https://connect.squareupsandbox.com/v2/payments \
    --header "Content-Type: application/json" \
    --header "Authorization: Bearer accesstoken112233" \
    --header "Accept: application/json" \
    --data '{
    "idempotency_key": "ab2a118d-53e2-47c6-88e2-8c48cb09bf9b",
    "amount_money": {
    "amount": 100,
    "currency": "USD"},
    "source_id": "cnon:CBASEITjGLBON1y5od2lsdxSPxQ"}'
My Retrofit call:
public interface IMakePayment {
        @Headers({
                "Accept: application/json",
                "Content-Type: application/json",
                "Authorization: Bearer accesstoken112233"
        })
        @POST(".")
        Call<Void> listRepos(@Body DataDto dataDto);
    }
DataDto class:
public class DataDto {
    private String idempotency_key;
    private String amount_money;
    private String source_id;
    public DataDto(String idempotency_key, String amount_money, String source_id) {
        this.idempotency_key = idempotency_key;
        this.amount_money = amount_money;
        this.source_id = source_id;
    }
}
And lastly making the retrofit call:
 DataDto dataDto = new DataDto("ab2a118d-53e2-47c6-88e2-8c48cb09bf9b", "{\"amount\": 100, \"currency\": \"USD\"}", "cnon:CBASEITjGLBON1y5od2lsdxSPxQ");
        RetrofitInterfaces.IMakePayment service = RetrofitClientInstance.getRetrofitInstance().create(RetrofitInterfaces.IMakePayment.class);
        Call<Void> call = service.listRepos(dataDto);
        call.enqueue(new Callback<Void>() {
            @Override
            public void onResponse(@NonNull Call<Void> call, @NonNull Response<Void> response) {
                Log.d(TAG, "onResponse: " + response.toString());
            }
            @Override
            public void onFailure(@NonNull Call<Void> call, @NonNull Throwable t) {
                Log.d(TAG, "onFailure: Error: " + t);
            }
        });
Retrofit Instance:
public class RetrofitClientInstance {
    private static Retrofit retrofit;
    private static final String BASE_URL = "https://connect.squareupsandbox.com/v2/payments/";
    public static Retrofit getRetrofitInstance() {
        if (retrofit == null) {
            retrofit = new Retrofit.Builder()
                    .baseUrl(BASE_URL)
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();
        }
        return retrofit;
    }
}
Edit 1: Changing to second parameter to JSON Object
JSONObject jsonObject = new JSONObject();
        try{
            jsonObject.put("amount", 100);
            jsonObject.put("currency", "USD");
        }catch (Exception e){
            Log.d(TAG, "onCreate: " + e);
        }
        DataDto dataDto = new DataDto("ab2a118d-53e2-47c6-88e2-8c48cb09bf9b", jsonObject, "cnon:CBASEITjGLBON1y5od2lsdxSPxQ");
 
     
     
     
    