MTS / Sistema Shyam TeleServices [SSTL] — Overcharging/unwanted use of bill charge - threatening calls/ poor customer service

Address:

Bangalore, Karnataka, 560033

MTS card no: [protected]

Initially I got the data card through an offer online which charged me 1299 for 1months usage and data card(both).
Date start 17 Oct 2015/

Which should be free for me for a month and thereafter bill generation of 999/- I suppose.

I stopped using internet from November 2015 after 15 days of MTS usage.

October 15th 2015 I started using, if you check you database and records.

You have gone ahead and charged me 625/- rupees immediately after 15 days which is not correct.

Next month I receive another bill 1678/- for which I didn't even use.

Could you please reconsider and check this error.

And give me the details.
I am very sure that I haven't used.
Plus my data card is prepaid.

I have message, bill payment and bill payment which show 625/- was due and you suddenly charge me after a month 1678/- which is not right.

I am really frustrated with the service and would like to raise a complaint against this system of bill generation.

I have all the proof to show you that what you have charged me is unethical practise or was it a mistake from your side.

And give me the details.
I am very sure that I haven't used.
Plus my data card is prepaid.

Kindly reconsider the bill payment is what I advised them in an Email.

Today I get a call from some unknown person advising me that they will be sending me legal notice if I don't make MTS payment for which I am charged for not even using and was very rude over the phone.

The MTS customer service is very poor and these ladies over the phones act abusive even though you try explaining to them, they don't understand the basic problem.

Plus today a person called and spoke to me in Hindi but the caller Id showed Karnataka but he's from Delhi I suppose.
Unknown caller number is who issued me warning +91 [protected]

In this care what should I do and steps/actions do I take against these calls where they don't even listen or understand?

And also please see the attachment added on to this complaint

Kindly help and assist