Bad Experience From TFG (Sportscene)

I am very disappointed in Sportscene and The Foschini Group. I purchased a pair of sneakers as a Christmas gift. However, the size was too small. I headed to Sportscene Rosebank Mall to exchange it and they had none in the colour and size I required. They let me know that Mall of Africa had a pair. At Mall of Africa, the pair they had on hand was held for lay-by and I therefore couldn't take it - even though I had fully paid. They told me that Centurion Mall had a pair. At Centurion Mall, the shoes and boxes were mixed up and the pair of White in a Size 6 that the system shows they had were a Grey pair in a White box. I would like to please be assisted by having a WHITE SIZE 6 of the New Balance Women's CT302 V1 White Sneaker (SKU ***1) sourced and sent to Rosebank Mall. I also have only until 05 January to exchange/return so I would like to be advised as well whether I should return the Size 5 in the meantime and then pay for the Size 6 once it arrives. I truly hope I can be assisted to resolve this horrible experience.