Yes, in the United States, it is legal to unlock your phone. The "Unlocking Consumer Choice and Wireless Competition Act" ensures consumers have the right to unlock their devices.
: Provide your IMEI and model (ZTE Z983) to the service provider and complete payment. zte z983 cricket unlock
A "SIM Locked" phone will not accept a SIM card from AT&T, T-Mobile, MetroPCS, or any international carrier. If you attempt to insert a foreign SIM, the phone will prompt for an "Unlock Code" or "SIM Network Unlock PIN." Without that specific code, the phone is essentially a Wi-Fi-only device on any other network. Yes, in the United States, it is legal to unlock your phone