Office London Pavillion refusing refund for purchases item

I bought vans sneakers at Office London Pavillion for my toddler , only to find that they don’t fit him. I couldn’t find the slip but I had a gift receipt, which I didn’t request since my son can’t exactly return a gift. Anyways, I work 3 hours from Durban and asked my partner to return the sneakers for me. I was told he can’t return them because he doesn’t have the original slip. Surely the gift receipt is proof enough that the sneakers were bought there. I called the Manager and was even willing to give them my bank statement as proof that I did purchase from them. The manager seemed to understand my story but he still couldn’t assist so the next best option, he said, was for his senior to get back to me. ... Christmas was over a week ago, I called around the 22nd/ 23rd December 2020 and nobody has contacted me yet.

As far as I know, having proof of purchase from a banking app or bank statement is proof enough for you to be able to get a refund. There is always some sort of code on the cellphone bank notification/ banking app/ bank statement that they can trace as proof of payment. Us showing them this is for them to trace on their side so they can find the purchase but not office London at Pavillion, they want the original slip. Worst part is that I’ve had this problem with them before and the very same manager was able to refund me. I wonder what exactly has changed this time