Checkers till error in customer's favour

I was undercharged by a three-figure amount when using my Checkers Xtra card today. I pointed this out to the cashier who was not really interested. I am not prepared to phone a call centre, and Checkers do not have an email address. The ball is in Checkers' court. If a Checkers employee reads Hello Peter posts, and Checkers want me to pay in, my Xtra card starts with 97100 and ends with 80506, and my name appears on this post.