IPhone T-Mobile Edge Problem

I have an apple iphone 8gb which has been unlocked and jailbroken and i am using a tmobile contract sim with web n walk on. It has been working fine until last night and the internet is not working on it. I keep getting an error message saying that safari cannot find server and my email cannot connect to my pop3 mailbox. any advice? nathplummer@blueyonder.co.uk