Disgusting service and misleading promotion

I complained on Twitter about one of the stores not delivering all the goods they had as a promotion I bought. I was told I didn't select the promo link. I then screen recording of how I placed my order. On Twitter they got back to me to say:" The promotion would have been labeled the same as the Flaming Wednesday promotion as per the video. You would have needed to select this to order the buy 2 get 1 free promo. As seen above the store you placed your order with did not have the option. We understand this is not what you were expecting and we apologise for the frustrations caused." They clearly know this was not my fault but the stores fault and refuse to compensate and give me my burger (which I don't want anymore) or a voucher/refund(due to their pathetic service on Twitter). I WANT MY REFUND.