Hi Serina and thank you for your questions!
Since the fee comes from Zettle, the first step is to contact Zettle to confirm that there's no issues from Zettle's environment. If everything seems correct from there, our support team will be able to help you look into this. Please contact our support team for further troubleshooting.
I hope the above is useful to you.
Please feel free to contact us again if you have any further questions!