I had same problem and after calling, discovered it its a monthly fee for a professional selling account on Amazon, which I never signed up for. Operatives told me it was a regular order and have been overcharged for a whole year and a half but never sold a thing.
Someone must have signed me up for it so call Customer Service and explain or check if you signed up to sell things.
The confusing part is Amazon place it on your bill as the same reference as selling an item, which is very confusing for staff and customers.
Ideally the should make those references separate from the regular buying items (main) website.
Hope this helps.