iPhone 5 unlocked but says no service,, tmobile nano sim

I got my iPhone unlocked off ebay and gave the guy my imei number. So after 12-24 hours I call apple and check if my iPhone five is unlocked they said yes. Now I got a tmobile nano sim and put it in my iPhone 5, then I restored it and iTunes said congratulation your iPhone has been unlocked. But for some reason on the top it's saying no service. I asked the tmobile guy at the store to double check if it was activated he said it was, he told me to call customer service I call them and they said there's nothing wrong with the sim its perfectly active. I tried restoring and setting it up again but still the same problem. I even asked AT&T and they said it is unlocked, and said tmobile are the ones who have to help me out and there's nothing they can do.I can't think of any solutions right now, so what's the problem??