I have a T-Mobile plan I signed up for in November 2013. I also have an AT&T plan with the contract end date of 5.01.14 . I brought my old phone to T-Mobile last November, but I'd like to update my other phone if I change over the 2nd line from AT&T. Is there a best way and most economical way to do that? Does T-Mobile have refurbished smart phones? (I couldn't find any on their website.)