You can block a contact to prevent them from calling you, sending you instant messages and seeing your status. In addition to blocking a contact, you can also choose to report abuse. This notifies us of spammers so we can stop them in the early stages of their activity.
To block a contact and report abuse:
Go to the Contacts or Recent tab, right-click the contact’s name and select Block This Person...
In the message box, tick Remove from your Contact list if you wish to remove that person from your contacts. If you want to alert Skype and report the contact, tick Report abuse.
Click Block.
The Block option selected in the Block this person window.
If you wish to unblock a contact:
In the main menu, select Tools > Options.
In the Skype Options box, select Privacy > Blocked Contacts. A list of blocked contacts is displayed.
Select the contact you'd like to unblock and click Unblock this person.