Pathetic Service in Pep Store 8353 with Manager Wendy

I bought my daughter Size 13 School shoes while She was on holidays.When she came back I found out they do not fit.I kept shoes in box with price But lost my slip at it was in December, so I went to Pep In Mqanduli for exchange the Manager Wendy said its never gona happen without slip. She said I must look around ask customers who are in store and ask them to buy me the size I want and exchange my size with them.I tried that and failed.Went to store again, following days was told to ask for customer who have bought the same shoes to give me their slip so I can get exchange that also failed as No one would give me slip as they might need it incase their kids shoes dont fit.After spending 2 hours in store begging customer for their slips,and exchange.I decided to go to Pep In Shopping centre just for last hope,to my surprise to get Their Manager Zan who said as long as the shoes have price and box and not worn she will do exchange for me.I would just want to know What exactly is This Wendy woman have against me as a customer because I went there more than once and she refused to help me.If I never went to another pep my child would went to school with torn shoes while I bought her new ones.