Can I get an Iphone 5 if I already have a Tmobile plan?

I already have a plan/contract with tmobile, I would like to get the iphone. Can I still get the Iphone from them and have it where i pay $199 down then $20 for 24 months even If I already have a phone plan with them?

Yes, you can.

It is $99 down and $20 a month for 24 months for the 16 gb, a little more for the phones with higher memories. Only the account holder can sign up, so if it is not your plan (even if it is your phone) you will need the account holder to sign up.

Note that the $20 a month is in addition to your plan.