Refund of unknown fee

I made a purchase on Amazon.com. Payoneer added a charge to the payment I did (something like a 1%).

I've returned the order from Amazon and will be getting a full refund soon. But I will making a new purchase as soon as I get my money back.

I guess Payoneer too will refund me with the money they charged me. Am I right?

By the way I don't even know what I'm being charged for (?). I thought make online purchases was free...

Any help will be appreciated.