cell phone Reminder alarm is not working?

Dear Sir,
I'm using samsung i320 from last two years. It was alright ,all functions worked from the beginning . Last few weeks reminder alarm is not ringing when reminder time set. reminder alarm set is on , alarm clock is on and it is working , phone call is coming and ringtone is ringing. please , tell me , where is the problem ?

Bazlul Karim Khan
December 2011