A User don't wanna give me back my money, how can i solfe this problem?

[ashur71]

Hi , i win a auction of a guitar, but i haved connection problem, and i can't play it, after in 28/11/2014 i try to buy it again in another auction but the dude saw that was me and cancell the roder when i pay it. Now the order is cancelled but on my email there's a message that yesterday the guitar was shipped, i cancello the order! When it wasn't shipped, and the dude don't wanna give me back my money. Help