If you're experiencing problems with your network, such as difficulty making calls or sending text messages, this may be due to a faulty SIM card. The SIM card for your device is located in the SIM card tray for easy access, or underneath the removable back panel. Sometimes, your SIM card will need to be removed or swapped with a different one. Before removing your SIM card, power off your phone, and have a small tool like a paperclip to help you take out your SIM card. Here's how to remove or insert a SIM card:
Locate the SIM tray.
Insert the paperclip (or whichever tool you're using) into the tray hole. It will pop out.
Pull the tray completely out, and remove the SIM card.
Place the new SIM card into the tray. Make sure you place the SIM card the correct side up to avoid damaging your phone or SIM card.
Carefully insert the tray back into the phone.
Once you've changed your SIM card, turn your device back on, and your phone will read the new SIM card information to connect it to the network. If it's a new SIM card, you might need to activate it with your carrier.