Very unhappy customer

I got the worst service ever from Woolworths Gateway(Durban) from a gentleman called Claude and a lady called Samantha. I bought size 4 shoes in Johannesburg on Sunday 01 July 2018,I wore them for the 1st time on Monday 02 July 2018 not even for an hour as they were hurting me,I suspect they are a small cut,as I usually wear a size 4 in all my Woolworths shoes(which is over 10 pairs). I took them back to get an exchange for a size 5 on Tuesday 03 July and then Claude and Samantha told me there was nothing they could do to assist me as they were worn. Im a loyal customer to Woolworths and have been very happy with their products but I am very disappointed in the way this situation was handled as I was not asking for a refund merely an exchange! Can management look into this matter urgently as I am on holiday and had only packed this shoes to wear to the Durban July this weekend.