this may or may not be something your intrested in but if you typ " scotch tape" in the serch box at the top of the page there is a fix for this problem. like i said u may or may not want to try it but ive heard it works.
i would deffinalty make a trip to att then, they are usually very helpful with this sort of thing. if it were me personally witch i don't know your full story i would do a general settings reset, and my phone is jailbroken so i would unjailbreak to see if that helped. lol but what ever the case, good luck.
Mine has also been doing this and I have not really thought much of it. It started with 1.1.3, but I don't know if it is/was 1.1.3 or 1.1.3 jailbroken. And I like my customization enough to deal with it instead of going back to stock.