Hathway Internet - Daily Spam Calls

I used Hathway Internet's home wifi plan for *-* months in Bangalore back in ****. I have since left the house. The new tenants moved in and continued using the same connection. They changed the registered number/details to their own number. To this day, I still continue to get spammed by Hathway on an almost daily basis regarding some plan or payment or god knows what. I have no pending dues. Whatever my bills were for the specific months where I used Hathway internet's services, were paid on time and Hathway team was told multiple times by me to collect the wifi modem from home.