Hitachi air conditiner - Air Conditioner defective

We bought Hitachi Air Conditioner Model No. RAW *** KUD **** from Vijay Sales last year in May ****, very soon we started facing an issue of knocking sound intermittently due to which the cooling is not effective, we made a request to attend our complaint at the earliest, the complaint was attended however inspite of product being in a warranty period we were asked to pay Rs *,***/- for which we still await the refund as inspite of * consecutive reminders the amount was not refunded.Again yesterday night i.e. *th of Oct we faced the same issue of knocking sound, for which we made the complaint, and have been informed that our warranty period has been finished which is three months from repair, so instead of assuring us a reliable service we have been informed that the call will be attended on a chargeable basis, we are extremely disgruntled by the non supporting attitude and shall not purchase any hitachi product in future.