To reject calls from people who are not SkyPrivate members, you need to log into your SkyPrivate account and go to:
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​Settings ⇒ Public Profile ⇒ Plugin Settings, select "Yes" at "Reject calls from users not on SkyPrivate" and " Save changes"

This setting will still allow people to add you on Skype, but the ones who are not SkyPrivate members will have their calls rejected instantly by the plugin.

   
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