Refund me back

So today 17/02/18 Foschini group has let me down again..did a laybye at foschini few months ago then it expired so that means they have to refund me but i lost my purchase slip ,when i went to foschini lakeside(where the laybye was done) they refused to refund me back because i didnt have the slip ,ok i let it go. So i had another at exact benoni lake ,i went there told them cant pay for the laybye anymore so they should cancel it,they told me i still got little extra month so i waited till i had money,today i went there to pay off the laybye and take it but when i got there they have already cancelled it three days ago ,so told them to refund me and gave them the prove of slips that i only had on me,i mean it has a date of purchase and every info but they requested the one i dont have ,lets just say they refused to help me yet again..it may not much but its still money,yet again its not about money its about people who refuse to do their job right (poor service) i lost my slip "how can you help get my money back" ?