Customer Paid More For Shipping Than The Shipping Price Is Set To

I am selling one of my products in multiple marketplaces. The shipping costs are set to a certain amount in the template. I noticed that one of my customers paid double the amount that the shipping fees are set to. I went to my product page on that marketplace and there it is – the shipping costs are double of what they should be. Has anyone had this issue? I am an individual seller if that matters