Refused to take a return item

To narrate the story I bought the air bed on 2 of June I opened it BUT didn't use it, only to find that they bought another one. Today I went to the store to return it the lady at customer service refuse to take it back saying the box is torn so no one will be able to buy it so they can't take it back, arriving at work I called the store manager she was not in I was transferred to the gentleman called Mike he told me that they can't refund me they can only give me a gift voucher. Why gift voucher I never use it,7 days is not over yet. I even went through the back of the slip reading their terms and conditions there is no part where they talk about voucher. What disappointed me the most was that, that lady didn't even bother to check if that air bed was used or not, she saw the torn box and decided not to take the item, of cause I can't fold it the way it was folded from the factory m not a machine. I'm very very DISAPPOINTED, to be honest I don't think I will ever ever do shopping at Game Mimosa not as long as I live, m hurt, m disappointed.....