Worst service ever

I purchased a dress for my mother 2 weeks ago.I lost the slip nonetheless I had proof of purchase as in the bank statement and the card I purchased with.I had to be told that due to the unrest they can't assist me.Surely a big company that like should have a back up system in place unrest or not.In a way you can't assist people who don't have an account with you according to the cashiers.The fact that I was given a we don't care attitude there's nothing we can help you with,The worst part is I just wanted to exchange to a bigger size ,I didn't want a refund.If we were all perfect,I think we should be all Billionaires.Because I lost a slip I should stay with a dress that I won't use that costed R500.00. The worst service ever I experienced at Foschini Greenstone and at Foschini at large didn't expect such a big company to have a lame excuse, when someone has all the proof.