customer dealing

I bought a spice stellar M 600 from konnagar spice hotspot on 30.09.2014. after one to two days I found out that the battery was draining in minutes and contacts was getting crashed. I contacted the hotspot retail showroom and after three to four days they exchanged me with a new spice stellar M 600. I opened the seal at the showroom only and after starting the phone I found out that the problem with the contacts getting crashed exists. I returned the phone at then only. Now I do not want to buy any other phone from there after getting harassed for two times. But they refuse to refund my cash and insist me to purchase phone from their store only. A staff named Sourav misbehaved continuously and not at all helpful.