Q: I'm trying to report a purchase that was not authorized by me but I can't get through. Can you help me , please?

Can you get through to your credit card issuer? 

The very first thing I would do is change the password to my Apple ID (assuming you are talking about a purchase at the iTunes store -- music or apps).  If you can't get help from Apple about this after a reasonable amount of time, take it up with your credit card issuer and dispute the charges.  Hopefully it won't come to that. 

One other thought:  Are there any other people who may have access to your account or the devices that access it -- roommates, children, that sort of thing?

How have you tried to contact Support ? If you haven't already tried both try the other of http://reportaproblem.apple.com and https://www.apple.com/emea/support/itunes/contact.html

After changing your password on http://appleid.apple.com : What to do after you change your Apple ID email address or password - Apple Support

(If you go via your card issuer you will possibly get the account blocked.)