MTS / Sistema Shyam TeleServices [SSTL] — mts data card services not working and want to close the connection

Address:

Sawai Madhopur, Rajasthan, 322001

I am using mts postpaid data card connection no. [protected]. It was not working for last 6 weeks and mts customer care also shutdown their service. But they send message to pay bill amount for last month for the non working internet connection. So i wish to disconnect my service but no body was there to resolve consumer problems they only sending message about payment for unused internet service. How to disconnect my service?