Bad customer service

I bought blinds for my window 2 months back at Pep Frankfort but they were too small for my window.

The manager explained that no exchange is allowed without a slip due to the looting and all which is understandable. The looting never took place in Frankfort. The manager knows that I bought them there and it does appear on my bank statement for logic’s sake, just the slip is the problem. I just need another width of blinds not a refund, I’m now stuck here with blinds that don’t fit!! I contacted PEP on social media and still nothing.