I'm finally contemplating of updating my phone. I would like to stay with my old plan which tmobile has labeled as 'unlimited blackberry' plan. (Unlimited calls and data). My current phone is Blackberry Pearl so at the moment I'm not really taking advantage of the data (except for reading my emails).
If I get a new unlocked or tmobile 4G phone (Android or Windows) from ebay, can I just put my sim card in the new phone? What would be my data speed? Would it be 4G or something else?