Airtel - Airtel Postpaid Bill Complaint

I travelled to Germany in the month of Dec ****. After returning back to my shock my Airtel bill for the month of Dec was Rs.****/-. On my inquiry I got to know that Airtel had activated international roaming facility so J have been charged this amount. But My mobile was switched off during my stay in Germany. I had only in * occasions switched on my mobile to access some data and during that time I got two incoming calls from some customer care nos, first incoming call I received was on Dec *th and the same was by mistakenly received which was for **seconds during and the second call was on Dec ** which is for * sec duration. Both the call were received by mistake. Now Airtel is asking me to pay Rs.****/- for Dec bill when I haven’t used my mobile neither for making calls, nor for messaging or internet usage. I think this is unfair to charge me such huge amount of money when I haven’t used my Airtel network internationally. Also I have registered complaints with Airtel and my issue is not being resolved and my outgoing call facility is barred. Now Airtel is asking me to pay for something which is didn’t use at all.