Stop the setrepeat of Android alarmmanager

I have created the alarm as shown below

Intent intent = new Intent(this, Areceiver.class);
PendingIntent sender = PendingIntent.getBroadcast(this, 1234567, intent, 0);

AlarmManager am = (AlarmManager) getSystemService(ALARM_SERVICE);
am.setRepeating(AlarmManager.RTC_WAKEUP, timenow, 3000, sender);

I created a button to stop the alarm. In the onclick method i have written the following code

Intent intentstop = new Intent(this, Areceiver.class);
PendingIntent senderstop = PendingIntent.getBroadcast(this,
            0, intentstop, 0);
AlarmManager alarmManagerstop = (AlarmManager) getSystemService(ALARM_SERVICE);

alarmManagerstop.cancel(senderstop);

But the job is not stopping. What might be the issue?