T-Mobile USA

I purchased a t-mobile phone there today around 2p.m. I had to retrieve a sims card for the phone. i had the phone about 3 hours. The phone wouldn't let me down load some things and it keep kicking me off line and when i would try to get back online it would tell me the phone wasn't capatible for usage. I was back at that store by 5:15 to return it. the salesperson informed me at that time "all sales are final" which was not mentioned at the time of purchase nor stated on the reciept. He wouldn't exchange the phone either. He did offer me an option of buy a more expensive phone and paying the difference. He proceeded to call some one on the phone who he claimed was the store owner. They began to converse in a different language. When i asked to talk to the store owner he refused to talk to me. He said he would be at the store at 6 p.m. I waited until 6:30p.m. he never showed