Nokia 2310 sending messages problem?

Hi, i have a nokia 2310, When i try and send a message it comes up "message sending failed" straight away without even attempting to send it. I have checked the message centre number and it is ok. I hav also tried inserting a different sim card which i know works so it must be the phone right? Is there anyway i can hard reset it? Or does anyone know the curee to my problem?
Thanks