Unacceptable customer service

I have a coupon for R5 off First Choice Butter Salted 500GR.<br> <br> Unfortunately when we wanted to use the coupon we were told that there were no stock and according to the staff on the floor the factory burned down. They did not want to give me a replacement for the butter and told me I cannot use the voucher.<br> <br> This is unacceptable and no options was giving as to what I could do.<br> <br> Please resolve.