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 tablet: touch 「Tablet」 app-> touch settings icon
![](http://tct-open-document.s3.ap-northeast-1.amazonaws.com/image/Tablets/南宫ng·28+TAB+10S/image10.png)