switch to Prepaid to Post paid connection

Hey there...

I recently order iphone with post paid connection and i already have ATT prepared connection. I want to continue the same prepaid number as postpaid. how i can do that?

my 2nd question is, i am expecting my new phone in another 2 or 3 days but i paid my prepaid bill 2days back. So is there any way i will get my prepaid connection money back? or is there any way i can hold my postpaid connection till my prepaid cycle completed?

i dont want to pay double billl (prepaid & postpaid bills) in the same month. Please help!!!

Thanks