Guess what happened - I kept blocking every offender and suddenly Microsoft locked me out of my account for more than 2 weeks. My Outlook, my Xbox, my Office, and many other paid services - gone! Why? Because, according to them, I had hundreds of blocked people! Well, there's no way to report for spam or scam - you can either delete a chat (they can message you again) or block them. At least these are the options on desktop. Skype has my contacts synced - why I don't have an option to block any contact from a person who's not in my contacts?! Or at least put them in second queue like Facebook Messenger does? Or allow messages only from people with verified phone? Of course, Skype is guilty as they don't bother to solve this problem.