Can I use my iphone with tmobile?

Okay I went through almost every video on youtube and the only thing I could do is unlock my iphone without a sim card.
I have an iphone 4 running on ios 6.1 or something like that.whatever.
anyways I was just wondering since tmobile has iphones now can I just ask them to give me a micro sim card for my iphone? Or does it not work that way.
because jailbreaking takes too much time and I couldn't take it anymore.
and everytime I did that redsnow *** like run as adminsitrator, the decrypt kernel message always shows up.
anyway, yeah can I just go to the people and ask them to set up my iphone or what?

Added (1). If I do end up taking it to tmobile, what would the cost be?
I already have unlimited internet and that 4g stuff but is there anything else i'd have to pay for?

I had AT&T and unlocked my iPhone 4S and told them I wanted to switch to T-Mobile and then if you don't know your serial card thing of your phone I think. You can get a new number but if you want the same number you have to call AT&T and ask them what is it. Tmobile gave me a card n put it in my iPhone + yes sign contracts an pay. So it was a better choise for me bc I couldn't use my iPhone Internet unless I pay And I didn't want to w in that plan. It's been better in Tmobile.

  • 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?