A SIM identifies your mobile service on a cellular network. It lets a compatible device connect using your plan’s voice, text and data services. Check whether your device uses nano-SIM, micro-SIM or Standard-SIM before ordering or activating service.

VoLTE means Voice over LTE. It carries voice calls over a 4G LTE network, which can provide clearer call audio and allow mobile data to continue during a call. Both your handset and your carrier/SIM service must support VoLTE, and the feature may need to be enabled in your phone’s settings.

Compatibility depends on your exact device model, supported LTE frequency bands, carrier VoLTE certification and software settings. A phone showing 4G data coverage does not necessarily mean VoLTE calling is supported. Confirm the model with your carrier and check that VoLTE or 4G Calling is enabled.