When the phone cannot make a call, the call fails, or the call cannot be connected, it is recommended to pay attention to the following aspects: 1. Check the signal strength meter on the display screen and check the network operation area map. If the signal is weak, move to an open location, if you are in a building, move to a nearby window. 2. Check whether the network selection settings are correct. Try manual selection, or try another network. 3. Check whether it shows restricted calls. If so, check the call barring, fixed dialing and closed user group settings. 4. Check whether the call fee limit has been reached and check the call fee situation. 5. If it still does not work, use PIN2 to reset the limit or contact the service provider.