I bought a plane ticket through Oppdon, and a week later they charged an additional €89.90 to my card. Apparently, during the ticket purchase I was automatically registered for their Prime membership, but I never received any information about this and I wasn’t even aware of it. This is a huge scam. On top of that, they are impossible to reach — I tried calling them 16 times before anyone answered. AND IT’S NOT FREE!!! The phone call cost me €20, and it led nowhere. So be warned! They are scammers!