2. Switch flight mode: You can try to switch flight mode, re-register the network and try again.
3. Confirm whether the mobile phone card has call barring service: Some operators have call barring service in their mobile phone cards. If the mobile phone card has restrictions on outgoing calls, some or all calls will be restricted.
4. Confirm the status of the mobile phone card: ensure that the phone bill balance of the mobile phone card is sufficient. If the phone is down due to arrears, please restart the phone after recharging successfully.
5. It is recommended to open the VoLTE HD calling service (contact the operator to open it): If the 2/3G calling network environment in your location is not good, you can contact the operator to open the VoLTE HD calling service and try again.
6. Comparative test: It is recommended to use the same carrier card to compare the surrounding mobile phones. If this happens, it is because the local network quality is not good, so you can move to other places and try again.