Worst customer service and return policy

I bought boots on Saturday the 1st of June and on Monday i wore the boots in the house to check if they are comfortable as i had sized up cause on Saturday my actual size was too tight. I realised then that the boots are a bit big and loose so i took them back to store on Tuesday 04/06 i was told the boots show marks and cant be exchanged. What must i do with R1200 boots that are big??? This is totally unfair and worst customer service. Iam so annoyed by how i was treated. Wha