I was wondering if its possible to buy a cheap Tmobile prepaid smartphone (not activate it) and use it on a Tmobile postpaid family plan? can i just stick my sim card from my (old regular cellphone) from my postpaid into a prepaid phone and it will work? all i want is talk (calls). my family has only talk on a family plan. i dont care about using texting or the web (data plan). i DO want to use texting (with google voice?) and web using wifi. has anyone tried this or know that it works for sure? you may be wondering why i dont buy one with an offer and the answer is i dont want to be bogged down with a 2 yr contract with a data plan. Thanks for any help!