Unhappy with service

On 25 Nov I bought tekkies from Mr Price Sport at Atterbury Value Mart. We live on a farm and luckily stayed over because the Monday I saw there's 2 left shoes in the box, size 6 & 7. The 7 was exchaned for a right foot size 6 without any paperwork or hassles.On 2 Dec I came to the city for business again and wanted to exxhange the 6 for a 7 since the 6 is too tight. When I got to the store it was loadshedding and all staff was sitting on the inside at the door. I knocked and they sat there staring at me, the first impression I got was that they are desturbed by me. A lady opened the door and I asked if they can please assist to just swop sizes as I live on a farm and can't come in again. She said she'll asked the manager who sat there eating and I asked if I could please talk to the manager. I feel it is very bad etiquette for a manager just to sit there with her food, she didn't even got up to talk to me. I explained to her that I live on a farm and are not coming back anytime soon, can't she please assist in any way and she just refused. I cannot believe that a big retailer such as Mr Price don't have manual systems in place to assist in cases like this. I didn't want to shop around, I just wanted the same shoe in a bigger size. She also said I should go to another Mr Price and I feel it is the responsibility of the store were I bought the shoes to assist me with my exchange. I might only come to the city again towards the end of December or beginning of January when we have business to do so by then I missed the 30 day exchange policy. Then they will probably also not asssit me because I missed the 30 days. I feel that if they really wanted to assist me, they would've made a plan. I just want to buy shoes from another retailer and get credit on the existing ones and never do business with Mr Price again.