2) Check whether there are smudges or scratches on your SIM card's metal surface as a defective SIM card may affect signal stability. If necessary, contact your operator to obtain a replacement SIM.
3) Check whether “Blocked numbers” or “Filter spam calls” is active on your phone: touch “Phone” app-> touch settings icon
![](https://tct-open-document.s3.ap-northeast-1.amazonaws.com/image/Tablets/TCL+10+TABMAX/image2.png)
4) Please try to recovery with turn on and off Airplane mode or reboot the device;
5) Please contact your service provider to check if any re-activate process needed for your service account.