The Straight Talk SIM card only works with T-mobile or AT&T unlocked or compatible GSM phones, as of May, 2015. A customers can determine her phone's capability by checking directly on Straight Talk's webpage.
Bring-Your-Own-Phone is a program through Straight Talk wireless that allows customers to bring a phone from another network carrier and sign up for service through Straight Talk. As of 2015, the only network carriers that work with this program are T-mobile or AT&T unlocked phones. The phones must be GSM-compatible phones.
In order for customers to determine capability, the Straight Talk website allows customers to enter some information about their phones, and Straight Talk then advises the customers if the phones can be brought over to the network. Once a customer is able to determine capability, she simply purchases a new SIM card for her phone with a service plan and activates it. Customers are then on the Straight Talk network.
Customers are also able to transfer a phone number from the compatible carrier to Straight Talk. To port a number, that number must be active with the current service provider. Customers can request the transfer and initiate the activation process by choosing the Activate option on Straight Talk's webpage.