Added shipping fee on items sold outside of the UK

Recently there is a shipping fee added to all of my cross-border listings (stored in the UK and selling in other EU markets) on top of the selling. I never set up this fee, and it isn't being charged to the customer either. The problem is that it's confusing my repricing app, which uses Amazon's API. The API indicates that there's a shipping fee, so my app matches other offers minus the shipping fee. For example, if the current Buy Box offer is 24.99, my app returns 21 because of the 3.99 shipping fee. I've contacted Amazon but haven't gotten a solution. If anyone can help me remove this unwanted shipping fee, it would be a big help.