I am going to buy an unlocked GSM1900band phone but i dont know how to get a SIM card. I have found all kinds of pay-as-you-go cards from Tmobile but i want to get one with a contract and my own number. Can i just take my phone into a T mobile store and have them put a sim card in for me? Because they dont carry this phone in their inventory, but it will work on the Tmobile Network....Im not sure how SIM cards work, i thought i read somewhere that a SIM is the same no matter what phone you put it in? If thats the case, can i just buy a free phone+plan from tmobile.com and take out the sim card they sent me?