Nokia 6790 Problem

I am a straight talk customer and currently use a LG290C phone and just purchased a Nokia 6790. I want to transfer my service and number over to the 6790, but have been unsuccessful. ST customer service says that the phone does not work in my area even though I bought the phone from Walmart in my area. ST also said I need to get a phone without a sim card. They could not answer my question why a phone was sold at a store in an area where the phone does not work. From what I can see I like the Nokia 6790 and would like to start using it. How can I get my service and number transferred?