Shocking service from Kurt Geiger

A couple of weeks I bought a pair of jeans from a store (Kurt Geiger-Sandton City) I trust. After one wash the jeans started tearing. I took the jeans back to the store to get an exchange but was told that they did not have the style of the jeans anymore. I was also informed that if I took another style of jeans I would have to pay the balance and that I could not be refunded cash as I did not have a original of the receipt (even though the store still had the copy of the receipt). I offered to bring a bank statement as proof of purchase and was told that would not suffice. I have been offered a gift card to use at Kurt Geiger or Spitz but I do not need anything from the stores. I am now being forced to shop at a store whilst I am not happy with the product I last bought there.