I checked a couple of your items and they are listed with Simple Delivery.
So, every time you sell an item, Ebay issue a label and charge you for it. Labels are not automatically refunded if you don't use them.
As advised, you can apply for a refund every time you buy your own label.
You have to complete a fairly lengthy form, add tracking, and apply within 14 days of the sale for each label you don't use.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)