Phone not Allowed #MM

[kamalSam]

a Sign of Danger with MM writen below. In notification showing Phone not allowed.
please suggest

[Nishitkohli]

Very nearly true- my opinion
is that please change the sim it is a sim problem. is it with airtel sim? same problem happened with oneplus6 of one of my friend he changed the sim and issue resolved. it is with airtel provider. if still problem occurs go to service CENTRE. maybe your device has been sim locked or do you have bought 2nd hand . first change the sim or restart or reset or go to service centre

[kamalSam]

yes it is Airtel SIM in 2nd slot.