Disappointed as a valued customer

I laybyed 2 pairs of shoes in September 2022 size 8 which m sure abt it the day of my laybye i got assisted by a lady & the size 8 was the last pair & the other lady who was working @ the same store was interested in size 8 too then only to find out it was the last pair.i fitted both shoes they were fine.on the 2nd week of december 2022 i went to the store to takeout the laybye which went well @ that time i didn't chek my stuff when i leave the till & the cashier also didn't chek the stuff with me on the till then i went home.Sunday the 10th of January i was home going to church when i took out the shoes only to find out that the shoes are size 6.today****h of January)i went to the store(Jumbo clothing) to ask for the exchange of the size 6 for 8 or maybe exchange with something.i had a problem of that i misplaced the slip which i looked all over the house i can't find it & i explained to them that i misplaced the slip then the store manager(Mpho) told me that i am irresponsible how cn i loose the slip.we argued & he called his superior Nosicelo Mokubjane i explained what has transpired then she told me that she can't help me as long as i don't have the slip then i asked them why when we don't have a slip when u come to takeout laybyes they give it to u with your ID why can't they do the same with my situation then she said no its my loss.my problem is m stuck with the shoes that are not going to be any use for me @ home in the name of i misplaced the slip? It was a laybye which i believe that if i give them my ID the dytem will show that i did a laybye of that kind of shoes & i've never worn them.i laid a complain @ the customer care & told them the whole story then they said they'll contact them & took my email adress & laid another 1 @ their headoffice they told me that they'll contact the store & the store will contact me i must'nt be far,after a while i got the call from the lady(Nosicelo) in the store telling me that she got the complain from the customer service to asdist me in paying the laybye even if i don't have the slip of which it was not what ive said i only wanted them to exchange the size to the proper 1.she hanged up.later again i got the call from the same lady(Nosicelo) saying that she got another call from their headoffice about the same story so even if i can complain to whatever place its still gonna be the same cause all the complains are going to be directed to her & there's no way she gonna help me as long as i don't have the slip why did'nt i go to Ackermans or Jet then out of anger cause ive been in the mall for 3 hours only for Jumbo & told her that she's now telling me nonsense then she hanged up the foun. I went back to the store accompanied by my son cause i took longer than i thot he was waiting @ the car.She denied calling telling me all those things she even told me that i can't expect them to run the store as i run my house hold.i left the store told her that m gonna write to hello peter then she said go ahead we'll see.i am really disappointed @ how the stores treat us locally.