Tikona — Threatening calls

I have disconnected from the service and returned CPE and other equipment already. I have also got a mail from the company stating that the amount payable is Rs. 0/- A month later I have got a bill! I called them immediately and they have told me I need not pay anything and asked me to ignore the mail. However, I have received a new bill on July 10th! Today, I have received a call from [protected] and [protected] stating that the company has launched a criminal and civil complaint against me over unpaid bill and that I will have to attend Delhi high court for legal proceedings. Even now, on Aug 30th I am receiving the same threatening call and they are harassing me. I have tried to contact the customer care..I am waiting for a long long time but unable to speak with them. I have communicated the same via. e-mail but no response yet!