Hathway — Terminate my Broadband connection and stop nagging me

I was having broadband connection number [protected].
I requested to terminate my account and returned my modem also. I am having the receipt and visual proofs for the same.
But I am continuously getting calls and messages asking me to renew my account and some offers.
What is the point of the calls and messages ?
I have mailed the same to your customer service and requested to stop these messages and calls. But you people are still nagging me.

I am requesting you to take proper action in this regard. Failing so, leaves me no other option except to proceed with legal action on you.

Thanking you