You may have had AT&T SIM (Subscriber Identity Module) card problems on your iPhone before or received the notification "Airtel SIM not provisioned." This happens sometimes, and the reason is fairly ...

SIM binding is a process where a messaging app verifies that the registered SIM card remains active in your device. If the SIM is removed, replaced, or deactivated, the app will stop functioning.

When you sign up for Tello, you will need to purchase a SIM card in order to activate your service. The SIM card is what allows your phone to connect to Tello’s wireless network, and without it, you ...

After you purchase and use your cellphone for an extended period of time, you can change networks. However, the phone that you're currently using may not be offered on that network. If you wish to ...