I have an att 4s, recently unlocked but it says no service even tho it shows tmobile under carrier?

I have an att 4s, i did restore and backup on itunes and got a congrats iphone is unlocked message on the screen. When i put my tmobile sim , it says no service, i tried different tmobile sims no service.i even got a new tmobile sim still no luck

But when i go under settings-general-about-carrier it shows tmobile 14.1 already, that means it s unlocked i guess ,but no ,still only works with att. What could be the problem?