How do I complain?

Since updating to the latest version of Skype (6.5.0.158) I'm constantly being sent invites from individuals not on my contact lists. Some of these individuals actually have pornographic profile pictures which is totally unacceptable.

 

I have my privacy levels set to my contacts only, so that obviously doesn't work to block these people. I am extremely unhappy, I sent a message to Skype with no response to date,

 

Microsoft should be making sure that this is not happening