Vodafone India — my vodafone plan is upgraded without my permission

Dear sir/ madam,

Last month 20/11/2017 my vodafone india has changed my postpaid ([protected]) plan automatically from 249rs/- to 399rs/- without my knowledge and permission
I have complained several time (Via chat and customer care support) to change to my previous plan 249rs/- but till date service provider not given any proper reply. Every time service provider says our support team will contact you in 24 hrs. But still date they have not provided any support or call back. This is like this service provider looting amount from there respected customers without any knowledge. May be this would have happen to many customers.
When i investigated my old bills, this service provider were charging extra rs20/- in every bill cycle from year 2011. Kindly understand customer feeling, we trusted, respected and believed that you will not do any change without customer knowledge and permission. We were using this service more than 10 years and we would have paid around rs 4, 00, 000 approximately till date. But this service provides has cheated us.
Kindly help us in taking strong action against this service provider.
Thanks and regards