Wanting to use my iPhone 4

A GSM Iphone uses sim cards and you can get a sim from TMobile or any GSM pre-paid carrier and start a pay by the month plan with data for those carriers - basically you are buying a fill card for the monthly amount and activating the phone. You just need to make sure that the no contract carrier will activate a phone not locked to their system. Most of them do. If your Iphone uses a micro-sim there are templates that you can use to cut a full size sim card down to size and there are several no contract/pre-pay carriers that will sell you a micro sim for the Iphone. My suggestion to you is go over to Howard Forums at www.howardforums.com and go onto the pre-pay, no contract forum and look at the various carriers. These forums will answer any question that you have to get your Iphone working on a pay as you go, no contract plan. Many, many there have done it.