Game warranty process.

Their is a Game in witbank, at Highveld Mall. There is an issue with a Microwave that we bought last year January. The box is still there but the slip has faded off. Problem came when they have to reprint the slip for us. They asked that we get a bank statement indicating the date it was bought as proof of purchase. Now they cant find the slip on they system. They not giving us any solution as to what should happen because the Microwave Has a 2 year warranty. Any advise on processing forward?