Hathway — Spam calls

Address: Chennai

Website: www.hathway.com

I have discontinued the hathway broadband connection and returned the wifi device 11 months ago. But still, I am getting spam calls threatening me that if I do not return the wifi device they will charge me and take legal actions. Not only this but I am getting spam calls for their latest offer and they keep asking me to take a new connection.
For the last 11 months, I am get these calls every single day, which is really frustrating and is taking a toll on my mental peace.