Hathway Broadband Internet - Hathway failed to refund deposit amount after disconnecting the service

I was using Hathway connection for quite a long time and recently when i moved to new location, i checked for setting up hathway connection there and hathway denied as there is no coverage in that location. So, I surrendered the modem and the executive gave me acknowledgement slip stating that i will receive the refund amount in fifteen days. Its been more than four month since i surrendered the device, but still get my refund amount.Also hathway executives call me daily without checking the database and force me to pay the monthly rechargable amount for the service which is already disconnected four months back and recently, this has gone to next level of sending me legal notice stating false that i did not surrender their modem. It would be very grateful if someone help me from their tortures as am posting this problem on representing many people who are facing the similar problem from hathway.