Please tell us some basic information before asking for help:
Hi, we'd request you follow the below steps:
1. Kindly check the same SIM into another slot
2. Use another SIM and see if the same issue persists
3. Use the same SIM in different device and see if the issue is with SIM.
4. If still you face the issue factory reset your phone after taking a full backup : https://www.asus.com/support/FAQ/1006346/
5. Last option would be to visit the service center
to have a check. Locate here: