Well I'm not sure which phone options you will have with your new carrier, but I for one have been a firm buyer of the Samsung slider-type phones. I prefer the slider to a flip-phone due to durability issues - my past flips have always broken eventually, or a wire inbetween the 2 pieces has shorted, or something crazy. I also don't like the small one piece type phones where the keys show because I tend to throw the phone into my purse or booksack or whatever, and they keys end up getting funky with purse lint, pushed at innopurtune times, or generally messed up. The slider phone protects the keys, and also slides out to make it a bit longer (ie. the mouth mic is closer to my mouth).

This is the phone I currently have...I'm on the second generation model, I think there is an even newer one out.

http://www.t-mobile.com/shop/Phones/...a-b298c1fa73ff