Cristovao, that is awful!
Talk to this guy:
ddiljohn@kobo.com
He'll get you sorted out. If you have an order number, he can get the charge on your credit card reversed for you.
Somebody at that call center very much needs to be fired, IMO. 'nuff said. Darrell knows all about my conversations with the call center staff, and it very much resembles yours.
Re your credit card--it can be pointed out, as well, that carrying a balance impacts one's credit rating, and not in a good way. Kobo needs to step up and fix this for you.