Lost 7500 rands at Hifi corp for a sansui fridge

Hi guys We did a laybye at hifi corp in West gate March 2016 paid abt 500rand the first month ..When we went back the next month to pay the shop had closed and there was notice at the door that just said customers must go to Strubensvale for anything they need.My husband went made payments for the next 5 months our laye was due October 2016.when we went to collect the Sansui fridge they told us we not on the system so they can't help us. Unfortunately I had misplaced the envelope where I kept my receipts but I had one receipt with the order number and the first payment slip. I also had the lay bye forms.we tried getting the fridge or our money back but they refused even to give the 500 rand that we had the slip for.we had paid 7500 rands till today they are quiet. We tried all we can and now the branch in West gate re opened but they say they can't help us. Is there a way we can get help guys I know that losing our receipt was a big mistake but I have something to prove that we made laybye in the first place. The funny part is when we checked on the system there was no record of our laybye even when we provided all the necessary information for them to check what happened. Please help us guys what do we do