Hathway Cable & Datacom — hathway threatening legal proceedings

I closed my internet connection with hathway in bangalore and moved out of india
I had raised a request for pick up of the modem device but it was never picked up by hathway
No i have relocated out of india and have no idea where the modem is.
Recently i got a mail from hathway asking to return modem to avoid legal proceedings
This has happened due to negligence of hathway and you should close the case automatically
Otherwise, i would have to raise an issue in relevant forums for customer harassment
My account number is [protected]