A:Answer According to Straight Talk's website, you can bring your phone from almost all of the major networks, so it doesn't matter if the 5S started on AT&T, Verizon, Sprint, etc. All you have to do is purchase the SIM from them and configure the new surface. However, if the phone is in a contract with a network, you will most likely have to terminate the contract and pay the fee before you can switch to Straight Talk.