I received an email saying I'm going to get $20 if...

I received an email saying I'm going to get $20 if I sell $20 worth of stuff on ebay. Then I sold 4 playstation 3 games so I can make $50 to get new ones. They ended up not giving me the $20 and charged me about 5-7$ on top of that. Also, they must have deleted my email on that account, because I couldn't find it anymore even though it was still in my email's inbox, but it wasn't on my ebay messages anymore. I also called them and they made it seem like I was lying when I still have the proof that they sent me an email. AVOID EBAY AT ALL COSTS! I'm going to put this review in as many places as I can so people know who they are dealing with.