Bad service

On the 28th of February, I bought a pair of shoes. I only wore it twice and yesterday I noticed it was torn on the side. It was the last pair they had. I returned the shoe yesterday and was told they could refund me and they had to book it in.

The procedure clearly if anything should go wrong I should be refunded or get an exchange and I had proof of payment but was still refused my money.

Can someone assist me in this matter as I am clearly not happy with the service at all.