Frustrated client

Foschini Cape Town CBD Golden Acre. I made a payment around 2015 to this store. This yearJanuary they phoned me to collect the same money I payed 3 years ago. I lost the slip because I have been moving addresses. I asked them to trace the payment because they asked for my ID when I made the payment. When I am enquiring this. They are telling me that they handed over my account to the lawyers 10 years ago. I asked them who do they inform about this handing over of accounts and why did they take my money if they knew the account was not with them anymore. Another thing i only knew about this account when i wanted to purchase a house and I went to pay. I was a student when I opened this account. I haven't received any concrete answers from them. I am really scared for old people with all this ***** going on. Why is Foschini *****ing from the poor while they are a multi billion company. Foschini i will not pay you twice. Yes I lost my slip I admit that. Is it also my fault that your systems are not showing my payment according to you? You are supposed to keep customer's data or information for 5 years. Why did u lose mine in 3 years?