Sterling Office Systems - Faulty Numeric UPS

I had bought Home Theatre Equipment from Sterling Office Systems located in Ameerpet (near Gurudwara) in December ****. As part of the equipment I was also sold a Numeric *KVA UPS which turned out to be faulty from Day *. The price of the UPS was Rs. *****. The UPS was taken back by Sterling folks and then returned after few days mentioning that they had repaired it and it was ok. It hardly worked for ** minutes and then stopped working again. Finally after numerous followups Numeric (product vendor) sent their service person on **th February **** and mentioned that the UPS was not working and would need to be taken back. They took the UPS back and since then I have not heard anything. I have been following up with Sourabh Kumar (sales person from Sterling, who has left the company) and Venkanna (owner of Sterling Office Systems) to either return the money or provide a new UPS in lieu of the defective one. Their is no response from them and they have stopped taking calls. Would appreciate if this can be looked into