Airtel — Not receiving calls from certain no's.

My cell no is [protected], Plz note from past 2 weeks Iam not able to receive calls fron ceratin No's like, [protected], [protected], [protected], [protected], [protected], [protected] etc. most of the no's are outside mumbai no's, when ever anybody is trying to call me, they get a message whether it is not reachable, or switched off, or out of coverage area.request you to plz slove the problem ASAP.