Verizon postpaid takes priority over prepaid. If a carrier has a roaming agreement with Verizon, they are prioritized 3rd. Somebody that has AT&T, T-Mobile, Sprint service is not using Verizon service and is not getting priority over you. If you have an android phone download an application called 'network cell info lite'. You can use the application to see exactly which tower you are connected to and what sort of connectivity you actually have, signal strength, which band etc.