Unlocked Iphone keeps dropping reception with tmobile?

[arthur G]

Ok i have a Iphone thats unlocked for tmobile now the problem is i put the sim card in and it stays on tmobile for about a minute and then drops one bar and drops another then goes to searching and finally to no reception?? after about another min or so the phone catches reception and goes back to full bars and repeats the previous stated problem? why does my phone do this? one person told me my phone was not unlocked the right way therefore not reading everything properly from tmobile? Im just curious if anyone else had this similar problem or if anyone has a solution for it thanks