The only way you can upgrade your phone, is to:
1. Pay full price for the phone you'd like. (no, they will not take your phone in on a trade for a lower price, nor buy your old phone from you for money)
2. If your contract is up, you can get a new phone at a discounted price. For example: If the regular price of a handset is let's say $400, with signing a new contract, you could get the phone for $199.
Those are the only ways I know of of getting a new phone unless you go to Ebay and buy a phone from there.
So to answer your question......no.