Eu li muitas perguntas e respostas no Stackoverflow, e muitas delas apenas enfatizam o.cancel() e o ID exclusivo especial. No entanto, agora importa quantas vezes eu tentei, eu não posso cancelar.

Meu ID único

final static int RQS_1 = 1337;

Minha função setAlarm. pickTime é Activity atual, e timesUp, é outroService classe que mostra um brinde quando o tempo acabou.

Intent intent = new Intent(pickTime.this, timesUp.class);
PendingIntent timesUpIntent = PendingIntent.getService(pickTime.this, RQS_1, intent, 0);
AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
alarmManager.set(AlarmManager.RTC_WAKEUP, targetCal.getTimeInMillis(),
                 timesUpIntent);
alarmManager.set(AlarmManager.RTC_WAKEUP, targetCal.getTimeInMillis(), timesUpIntent);

Minha função cancelAlarm

Intent intent = new Intent(this, pickTime.class);
PendingIntent timesUpIntent = PendingIntent.getBroadcast(this, RQS_1, intent, 0);
        AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
        if (timesUpIntent != null) {
            alarmManager.cancel(timesUpIntent);
            timesUpIntent.cancel();
            Toast.makeText(getApplicationContext(), "Alarm is cancelled",
                    Toast.LENGTH_SHORT).show();
                    } else {

            Toast.makeText(getApplicationContext(), "Unable to stop timer",
                    Toast.LENGTH_SHORT).show();
        }

Meu tempoServiço

public class timesUp extends Service {

    @Override
    public void onCreate() {

        // TODO Auto-generated method stub

        Toast.makeText(this, "MyAlarmService.onCreate()", Toast.LENGTH_LONG)
                .show();

    }

    @Override
    public IBinder onBind(Intent intent) {

        // TODO Auto-generated method stub

        Toast.makeText(this, "MyAlarmService.onBind()", Toast.LENGTH_LONG)
                .show();

        return null;

    }

    @Override
    public void onDestroy() {

        // TODO Auto-generated method stub

        super.onDestroy();

        Toast.makeText(this, "MyAlarmService.onDestroy()", Toast.LENGTH_LONG)
                .show();

    }

    @Override
    public void onStart(Intent intent, int startId) {

        // TODO Auto-generated method stub

        super.onStart(intent, startId);

        Toast.makeText(this, "MyAlarmService.onStart()", Toast.LENGTH_LONG)
                .show();

    }

    @Override
    public boolean onUnbind(Intent intent) {

        // TODO Auto-generated method stub

        Toast.makeText(this, "MyAlarmService.onUnbind()", Toast.LENGTH_LONG)
                .show();

        return super.onUnbind(intent);

    }

}