Can i get an iphone with tmobile?

I have tmobile and i got a galaxy s2 and the new iphone just came out and i want it but i want to know can you buy a new phone but keep the plan and conctract that i have? And if i choose to buy an iphone with no plan or anything just the phone can i? How much will it cost?

Sure, you can pay full retail price for the iPhone 5 for $580 (16gb) or $680 (32gb)