I want to buy a unlocked/jail broken iPhone off of eBay, but I want to make sure I can use it with my current t-mobile plan.. Someone told me that there is no where to put a sim card on a iPhone..
You can use an unlocked iPhone with a T-Mobile plan. However, if it's a 3g or 3gs, make sure you never upgrade to OS 3.1 on iTunes since you'll probably permanently lock the phone.