Unfair treatment as much as they value their shop I also value my heard eaned money

I made a lay bye at pep keywest for -+-900 worth of clothes, only to find one of the items wasn't the correct size, I went back to exchange couldn't find the same thing so I asked for a refund for that 1 item, I was then told I can't since I don't have the slip with the item on so I can only exchange, went back the following day took one item to exchange was told I can't be helped since its not the same amount, I had all the other pop proof that I bought the staff there except that one slip that was never given to me when I went to take out my laybye. The ladies where practically forcing e to take something else and I wasn't interested, I am a regular customer there and I feel this is very unfair and unprofessional, they can always go to the system and reprint but they didn't. Bother to do that all I was told is that they can't help me, mind you standing on that long queue only to get service like this spending my petrol to drive there 2 days in a row I was very annoyed by all this.