Object telephonyInterface;
Method methodEndCall;

...

TelephonyManager telephonyManager = (TelephonyManager)getSystemService(Context.TELEPHONY_SERVICE);
PhoneStateListener callStateListener = new PhoneStateChangeListener();
try {
	Class<?> classTelephony = Class.forName(telephonyManager.getClass().getName());
	Method methodGetITelephony = classTelephony.getDeclaredMethod("getITelephony");
	methodGetITelephony.setAccessible(true);
	telephonyInterface = methodGetITelephony.invoke(telephonyManager);
	Class<?> telephonyInterfaceClass = Class.forName(telephonyInterface.getClass().getName());
	
	methodEndCall = telephonyInterfaceClass.getDeclaredMethod("endCall");
} catch (Exception e) {
	e.printStackTrace();
}		
telephonyManager.listen(callStateListener, PhoneStateListener.LISTEN_CALL_STATE);

...

private class PhoneStateChangeListener extends PhoneStateListener {
	@Override
	public void onCallStateChanged(int state, String incomingNumber) {
		switch (state) {
		case TelephonyManager.CALL_STATE_RINGING:
			Toast.makeText(getApplicationContext(), incomingNumber, Toast.LENGTH_LONG).show();
			try {
				methodEndCall.invoke(telephonyInterface);
			} catch (Exception e) {
				e.printStackTrace();
			}
			break;

		case TelephonyManager.CALL_STATE_OFFHOOK:
			break;

		case TelephonyManager.CALL_STATE_IDLE:
			break;

		default:
			break;
		}
	}
}