Are you seeing these “ads” at the bottom of your Contact List? If so, then these are only “Alerts and messages”.
In Skype go to Tools -> Options -> Notifications -> Alerts & messages. Uncheck the options: “Help and Skype tips” and “Promotions”.
You should not see any ads at all with Premium account. Can you make a screenshot of this add playing in your Skype Home page and attach this screenshot here?
Hi, Rita 201072,
As Ruwim requested, above, please post back including a screen shot of the advertisement which is appearing (please "white out" or redact any personally identifiable information). Please also confirm you are indeed a Skype Premium subscriber.
Online Safety Tip: Change your passwords often!