Don't buy from Mr d food

Yesterday I received a gift voucher from a relative, there is no instructions in sight when accepting this voucher. Since there was no instructions, one automatically assumes that when placing an order, it would deduct off the voucher and not my account, right? Wrong. Mr d food refuses to take responsibility for this and won't refund and just take the voucher off, they claim they don't have the money for the voucher, even though money would have been received for them to issue a voucher and insist they cannot just take off a voucher, which is probably another lie. All of this while I've been unemployed, and the reason I was given a voucher by someone. You've lost a regular customer and I hope this post will deter others from giving you business, since you will happily take money from someone's account that desperately needs it for other utilities.