Poorest service I got at Mall of the North

I bought Volcano bluetooth head set at game and they did not work, I returned them at Game Mall of the North! So apparently they do not do direct exchange but give you the same amount voucher back then you decide wether you buy the product again or take your money back. I went for the headsets again, first_they refused to let me test them before I buy them, when I get to the till the cashier says the price has gone up I have to pay the balance, but I refused because from my knowledge I am suppose to get them for the very same price, she got so mean that I just asked for my money back and left.