Any fees you pay are set and collected by who you are paying via the Paypa Plane software.
You may be charged fees for transactions, late payments and even changes to an Agreement (such as processing day change), etc.
All fees are clearly listed and displayed in the “fees” section of your Agreement (scroll down to "Description").
It is important to note though, that Paypa Plane is a software provider and does not directly charge you any fees.
As such, any fee queries should be directed to who you are paying, their contact details can be found in the “Contact” section of your Agreement, or in the “Support” section of the menu.