java - Drop incoming call

Question

I'm trying to block incoming call in android. I have this BroadcastReceiver but it handles the incoming call but does not block incoming call on my android 2.3.6 phone(didn't try on other versions). here is my receiver:

public class PhoneCallReceiver extends BroadcastReceiver {
    Context context = null;
    private static final String TAG = "Phone call";
    private ITelephony telephonyService;

    @Override
    public void onReceive(Context context, Intent intent) {
        Log.v(TAG, "Receving....");

        TelephonyManager telephony = (TelephonyManager) context
                .getSystemService(Context.TELEPHONY_SERVICE);
        try {
            Class c = Class.forName(telephony.getClass().getName());
            Method m = c.getDeclaredMethod("getITelephony");
            m.setAccessible(true);
            telephonyService = (ITelephony) m.invoke(telephony);
            // telephonyService.silenceRinger();

            telephonyService.endCall();
        } catch (Exception e) {
            Log.v(TAG, "failed....");
            e.printStackTrace();
        }    
    }    
}

and the ITelephony

package com.callblocker.mk;

interface ITelephony {

  boolean endCall();

  void answerRingingCall();

  void silenceRinger();

}