Where to buy a lower price cellphone that I can use for my T-Mobile?

My Samsung SGH-E635 I very weak signal while my Sony Ericsson K700i is better but the cursor is defective, I have seen Nokia inexpensive by Ebay, says Cingular 2125 Smartphone Quadband Worldphone, ask the seller if released on but he just asks me read & review Spec. phone, I admit its locked, it is easy to unlock, where & As, any brand & suggestiowhat; model? I want with the cam, & bluetooth; small