Mahanagar Telephone Nigam [MTNL] — excess billing in my mobile number

Address:

BKC, Mumbai City, Maharashtra

I have been using dolphin mobile service of mtnl for several years. Account no.[protected]. My mobile bill has never exceeded 500 rs any time. Suddenly in jan 2019. My bill is showing unreasonably inflated amount of rs 7976. I was asked to pay this amount by 22/2/19else the phone number would be suspended. My phone was suspended on 22/2/19 i was asked to pay at least4000/ so phone would be connected which i did.. On enquiring i was given rediculous replies that when both wifi and data is on the bill gets enhanced. Till now it was never the case why now? Why cheat customers for some technical fault. I want the correct bill and excess money paid refunded.
And correct bill t