The phone does not ring at the certain number
Iphone 7. IOS 11.2.6.
The call does not go to a certain number and also does not send the messages. I can’t call and send messages only on this number. My number is not in the black list. Also I changed SIM but this error appeared again (SIM cards belong to different operators).
When I call from another device, but the same SIM card's, the subscriber sees and receives the call.
To solve the problem, I restarted the device, used another sim card, and reinstalled the firmware from 10.3.3. on 11.2.6.
It did not help. How should I solve this problem?
iPhone 7, iOS 11.2.6