Refusal for exchange/voucher

On the 9th Dec2015, I went shopping for items worth R2 357 which included shoes at the Waterfront.I am usually a 38, but when I tried them on again it was tight, and i then knew i had to return it.I had never worn the shoes again.I asked the teller why the shoe had marks underneath and she said its because its on the floor and people are trying on the shoe all the time.I didn't mind because I had no intention of returning the shoe. On Dec16th 2015 I went to Zara at Warmer Park in Port Elizabeth to do an exchange or get a voucher for it. All I wanted to do was exchange it for something else,not get my money back but they wouldn't budge! I was told that the shoes had been worn and they could not help me.The managers was extremely unhelpful and unapologetic.Although I have always been a frequent shopper at Zara this experience has left a very bitter taste in my mouth.I left the shoe with the store manager.The shoe also did not have a tag on it which I only noticed when I was returning it and they informed me of it. I am aware that ZARA has cameras at their till points that will clearly show that the shoe had no tag and it will show me questioning the teller regarding the marks.