MTS / Sistema Shyam TeleServices [SSTL] — Data card deactivation

Address:

Chennai, Tamil Nadu, 600126

I have requested for the de-activation of my data card # [protected] in the first week of may 2016. The same got deactivated on 10th May, but without my request/knowledge, the same got activated again on 18th and they are claiming the bill amount for that. I have sent so many mails to customer care, called them so many times, but no action has been taken to close the account and send the revised bill. I have been working in telecom sector for long and even if I face these kind of issues from MTS, I can imagine how will they exploit the common people.
Also, they had a long history of changing (reducing) the data limits of the on-going plan without even notifying the customer. They did this at least two times.