fastway cable bathinda - Set top box not working fine

From many days cable not working fine. Channels output is lagging from one month, video output is stopping for *-* seconds, after am complaining it to the cable vendor they told that HDMI cable coil of Fastway hd settop box is needed to changed although box is need to changed and they are demanding *** Rs for new set top box. Is this valid as it is the responsibility of cable operator to give these kind of service at their own cost for consumers point of view also when we purchased the fastway set top box we give them refundable security fees of set top box and saying it will return when we close cable operating with customer. Please respond