Does Sprint have different motherboards for Pre-paid phones?

just purchased a new Sprint motherboard for my phone but there is a problem. Your mother board works fine, but I guess Sprint made their pre-paid phone motherboards differently as I tried unsuccessfully to hook up to their network for about 3 hours. I finally gave Sprint the IMEI number and they stated that motherboard is for a regular plan and not a pre-paid device. Do you know what is different between the boards or is Sprint lying to me?