I have a AT&T "GoPhone" simcard in mine (8Gig Iphone) without a data plan. The thing is, that the iphone comes with EDGE network which kicks in if your in an area where you can't connect to wifi and they'll charge you by the kilobyte which can add up. I got soaked for about $14.00 for about 15 min of web surfing at a hotspot before I realized what was going on. There is an App you can load once it is jailbroken called Boss Tools I believe that'll shut it off for you or you can SSH into your iphone and change a couple of things that will render it useless. I did the latter and there are tutorials for both if you search for them. I would suggest using Boss Tools unless you know what you're doing as far as manipulating files goes. Either way, make sure you do your "homework" before attempting any modification. Good Luck.
