It is suggested to check:
Check whether the mobile phone is overdue and shut down. It is recommended to pay for recharging;
Check whether the mobile phone has set call forwarding, flight mode, call restriction, etc. It is recommended to cancel and try again;
Check whether the phone function or signal is normal. It is recommended to change the phone or location and try again;
If roaming to other places cannot be used, it is recommended to check whether the local network signal is normal and whether the number has opened roaming permission;
Try to restart or change the mobile phone to see if it can answer or make calls;
Take the mobile phone card to the local business hall for inspection or replacement.
If not, contact the local customer service.