T-Mobile monthly. Needing advice about returns policy on a phone that I might regret?

I just got a t-mobile contract with a free Blackberry Curve 8520. It is due to arrive tomorrow, and looks nice but now I am afraid that I may not like it. My eyes have taken an interest on the blackberry bold 9700. But the problem is what happens if I really want the other blackberry? Because I know there is a 7 day return if you are not satisfied with the phone, but it doesn't mean you can exchange it for another one and also you would still have to be paying your tariff. So how can I go on about exchanging the phone if I am not satisfied? Or do I have to buy the 9700 out right on handset only and tell t-mobile of my new handset? But doesn't that in turn alter your contract?
Please someone let me know. And no rude comments as I will only delete. Thank you.
 
Back
Top