No return policy

How is it possible that my husband buys me a pair of shoes yesterday morning from liberty midlands mall pmb. I try them on at work and they a bit to small and I put them back in the box to return today and get a size bigger only to get told that they can’t take them back because I have used them. And that they are soiled with dirt! Seriously???????? Surely when u try on a pair of shoes u have to walk a bit in them. So I seriously find it hard to understand this. Please could u advise?????!!!!!!! Also for the manager to give the customer his name and to say to a customer that we can try and challenge him. This service is appalling. When customers try shoes on in the shop they walk with them. I wasn’t able to go to the shop so could only try them on at my work