Bill settled in 2016, after 2 years now getting calls again for payment

MTS Bill settled in 2016, after 2 years now getting calls again for payment:

I had taken MTS data card connection and their service was so pathetic as I was just not able to get stable connection with good internet connectivity, I asked them to cancel the connection. Until the cancellation request, I did not have any pending amount all was clear. But MTS did not cancel, they said they will rectify and send a technician. A technician came and confirmed there is technical issue but did not rectify. I kept requesting for cancellation but they did not cancel and kept billing me. I did not pay and they started harassing me pretty bad. I used to get nightmares by their calls. Since I understood that there is no point in talks with these ppl, I made the payment based on their amnesty email. I sent an email to them with the confirmation that I have paid, but I did not get any reply nor a cancellation letter from them. But everything stopped since then. This was on November 22, 2016. After 2 years, now on Nov 3. 2018 I get a call from Cyber Police of Kolar stating I have dues to be paid, if not, they will file an FIR in Delhi court and I will have to go to Delhi court and my documents will be seized so that none of the banks will honor me and if I do not want this to happen, they are asking me to pay. The phone Number I received call from is +919739766558 .. I have asked them to send me the case details/letter for which they said it is not yet filed, they will file and send it. Please suggest me what to do. I am thinking of contacting my local police station , would it be a good idea or do I just wait for these guys to send me the letter or any case details?