Poor service from Great Sound

Poor service. From this Great Sound montana . Our TV was damage and we lost the slip the only thing we have is bank statement and the box that shows the despatch date .when we go to them they tell us there is nothing they can to retireve the slip because their system is crushed . So it's been 3months and our hisense tv is not working because hisense requires proof of purchase . Great Sound is bad it was my second TV buying from them and I will.never ever go buy anything from them again . HOW DO YOU TELL THE CUSTOMER THAT THE IS NOTHING YOU CAN DO TO GIVE SERVICE . can they not do something to help us with hisense and proof of purchase as we have proof of dispatch and bank statement