Airtel - Wrong postpaid bill from airtel

Dear Team
I have been associated with Airtel Postpaid for last * years. I am on business travel to UK and kept my plan to minimal of **rps for the last two years. All of a sudden i could see the bill for Sep ** as ***** rps..when i check with customer care, they said i had actived IR plan.. I tried to convince my best that i never enrolled any plans and there is no email or message status this Plan is enrolled.. i am currently in uk and never used my indian sim for any outgoing or incoming calls for the last * years..i tried to reach out them in email, calling them (spent almost *+hrs), twitter, insta, fb..but no proper response..its creating a mental stress by seeing bill from *** rps to ***** rps..its really frustrating ..tried my best for these * days from day * of the bill..but airtel never bothers..i am open to walk way from airtel framework, but the way they are treating me is quick not acceptable.