Can I use an AT&T iPhone with tmobile?

I have an iPhone 4 and the carrier is AT&T I was recently told that my iPhone is locked by a dude that's not quite the expert, anyway I was wondering if I can activate my iPhone with tmobile even if it's locked to AT&T since they share the same type of network

No the phone can't be used if it's locked to a different cellphone provider unless you do get it unlocked

  • Is the tmobile iPhone 5 already unlock? And will the tmobile 5 work on AT&T? I have recently been looking at buying an iPhone 5 and I found someone, but they have tmobile an I have AT&T. Will it work on AT&T? Also, how much would the newer SIM card be?
  • Do Tmobile iPhone 5's work with Tmobile prepaid sims? I know its a pretty stupid question but I'm about to buy a used iphone 5 and I'm taking every precaution. So does the phone need a tmobile contract or be unlocked? Or will my prepaid sim work in the tmobile iphone 5?
  • Can you use still use the sim card from tmobile in this situation? I've been wanting an iPhone in my whole life, so i got an Alcatel One touch fierce, tmobile contract, uder my father's credit, so i have given a thought of buying an iPhone 5s in full price and ill be purchasing it on apple store. Is it possible if i use the sim card from tmobile and use the iphone as my phone? Is that possible?
  • Can i use my 4G TMobile service on an IPhone 4? I have a TMobile Sim card that i used in my old phone and it got 4G internet but that phone broke so i had to use my little brothers IPhone 3G. It worked because we unlocked it, however, it was only able to receive 2G internet and i'm assuming its because of how old the phone was. My parents are buying me an IPhone 4 for christmas and they wanted me to put my TMobile sim card into the phone and unlock it for the capabilities. Will i be able to get 4G internet on it though?