Hathway Cable & Datacom — invalid invoice and complaint on me

I have a Hathway connection once and their service is not good so i decided to cancel the subscription and paid all the amount remaining and informed them about via mails and everything . Their representative come to my home and collected all the cables and everything and gave me the acknowledgement for device collection..

After that everything was over they again charged me for the next month for billing which i didn't used.

Today someone called and said Hathway filed a case on you and you should pay the bill.. So i am complaining that here.