Bharti Airtel - Infringement of consumer rights

I m a prepaid airtel user for past * years .
Last week airtel sends a sms about increased call rates and that my unlimited full talk time plan that was recharged on ** August **** had been defined to be valid till ** th November **** beyond which a new recharge has to be made to avail the current balance Also ,if a recharge wasn't done till ** days then the incoming calls will be barred as well.
At the time of purchase this connection was life time validity and free incoming .

Contact centre, Nodal office and Appellate authority...all have same a swer and that they can not do any thing about this.
Although the amount is small but considering that more than ** % of airtel are prepaid consumers and majority of which opt for full talk time plan .So the collective amount is beyond imagination which will go straight in their vault.
I asked for a reference no or complain number , but they say that a complaint no cannot be given as this is not a case to be considered.
I have a mail trail that can be shared .