Hathway — For Receiving Threat Calls

I had taken internet connection November 2021 which got expired in March 2022, while shifting I had asked the person who gave connection to take back the router and after a week also I called and told him to take the modem from room. He said not to call again as he will collect the modem. Now I am getting threat calls pertaining to modem not returned from some Hathway Pre Legal Team. They are asking me to pay the modem charges because as per their record it marked as not returned. Once over call I had informed about this too. Team said they'll take care. Now this nuisance has started by sending threat emails, I am ok to receive the legal notice and I will handle it myself but why create such nuisance by sending emails or calls