MTS / Sistema Shyam TeleServices [SSTL] — MTS is demand payment for the service that didn't work even for one second

Address:

560061

Mts has been sending me notices via sms about rs. 1800 that they say is due.

I asked them the following:

1. Copy of the invoice when the sale was made to me.
2. Copy of the agreement that was signed by me
3. My usage report

They don't have any of these. But they keep calling and sending message about court appearances and it has been a big harrassment.