Yes you can.
I suggest selling it on craigslist.
Restrictions:
- You can only use a T-mobile phone or an unlocked GSM phone.
- Your data plan is a 1 year contract. you cannot remove it from your contract for 1 year from signing the contract. So I suggest getting a cheaper smartphone.
Some phones take SIM cards or microSIM cards. If the new phone you get does not that the mircoSIM just to TMO and make them change it (they may charge you 20 bucks). If they try and charge you go to Costco and they will change it for free.