Hi and welcome to the Skype Community,
With your Xbox One came the "Best of Skype experience" free offer for 6 months. Details here: https://support.skype.com/en/faq/FA12393/what-is-t
And just to add a bit more clarity - there will be no recurring charges after 6 months come to an end.
OK. But I had to unlink and relink my skype account to get it lined up with the right Microsoft account. And in the process, the premium upgrade disappeared. When I had Premium, I could contact support via chat. But now it is gone---and adding insult to injury I can't contact support to ask for help!