Stick it out with T-Mobile until your contract is up for 1, Unless your service is really crappy. (which mine was here on the east coast, why i switched back to Verizon) But GSM phones have so much more compatibility and you can get an UNLOCKED iPhone to work on Tmobile, as well as any ATT phone. Might have to pay full price or get the phones used off ebay/craigslist etc.
But only benney i had with TMO was the customer service. But i never had service and i got tired of that so i went back to a better carrier (IMO).
i3-2100, 8GB, 90GB Vertex3, 1.5TB HDD, HD6850OC, 23"ACER LED Monitor (Gaming Rig)
1.83ghz Macbook 1,1 (School work, Websurfer)
4GB Mini, 2GB Nano, 30GB Video, 8GB iPhone 3GS, iPad1
BB Bold 9900