Krzr K1 problem with searching service

Hi,
I just got a K1 from eBay, unlocked, when I first put my sim from T-mobile, it could not find T-mobile service while my wife phone (also T-mobile) showed 3 bars. I went to network setup and select new network, after a couple of seconds it found Tmobile and registered successfully. Worked fine as long as the phone was on. But after I turn it off and on again, it failed to find t-mobile service and show "No service". I had to do it manually by selecting new network as before, and it found and registered to tmobile again and worked, this happens every time I turn it off and on. Don't know why, please help. Otherwise, I can not delete the network list, I really can if the phone is on, and the list came back after I turn it off and on. so weird!

Anyone out there please help me! Thanks too much.