I recently purchased a Skype Online number and could not figure out for the life of me why I kept on getting the message "The number you have dialled has not been recognised.." when I tried to call it. It seems there is a Skype privacy setting that doesn't appear to be on the FAQ's on the Skype site. If it is a I must have missed it.

In the Skype client go to Tools > Options and then click on Privacy and then on Privacy Settings.

Ensure that Allow calls to my online number(s) from. is set to "anyone". In my case it has been set to "phone numbers in my Contact list only". After changing this setting I was able to receive calls.