MTS / Sistema Shyam TeleServices [SSTL] — Mts mblaze data card

Address:	Salem, Tamil Nadu, 600089
Website:	www.consumercomplaints.in/new_complaint

I took an MTS data card connection (no: [protected]) on 2015 and been using it since. Last 4 months am facing difficulty in connectivity of device. In July 2016, I had to pay Rs. 1, 910/- . The amount was for 3 months and I used the data card only for 1 month. (My monthly rental is around 600 Rs.). Customer care executives had called me for bill amount collection and when I explained to them that I have not been using the same since 2 months due to connectivity issues, they simply told to pay the amount.
Further I raised a complaint with the team. One person came from their team and the line was activated for a few minutes for checking connectivity. After checking, the person told that the issue was due to signal and not with the device and left without telling anything. Further no communication was sent from them. Without any way out, I had to pay the entire amount after they threatened that they would take legal action.
The same problem has repeated again. I haven't used the data card for 2 months now and my bill keep generating. Yesterday I spoke to a person who offered me a waiver of 300/- Rs. if I pay the amount on the same day. When I refused the person connected me to her higher official and that person took a complaint. Person from complaint team had called and registered a time to visit tomorrow (24th Sep 2016) morning to address the issue.
Today morning i again got a call from them saying " Sir, we have registered complaint. So, at least please pay the due amount so that we can activate the line when our person comes tomorrow". I replied to them in negative stating that I won't pay until the issue is sorted. The lady kept calling me but since i had to attend a meeting i cut the call.
Afternoon am getting a message from "RM-OVERDU" that advocate notice has been issued against me for non-payment of bill.

My Questions are below:
1. How can MTS initiate advocate notice when a complaint raised by them against my data card number is still active and not closed.
2. Without giving prior intimation how can they initiate a legal complaint me?
3. I had not refused to pay the amount. Instead i merely stuck to my statement that once the fault has been identified and addressed I would pay the amount in full.

Kindly look into the case. MTS is the worst sort of service provider one can ever imagine.