Users who sign into Microsoft Solitaire or Microsoft Mahjong games for the first time, automatically receive one week of Premium for free with no strings attached. All you need to do is sign in using a Microsoft Account and you will get all the benefits of Premium for 1 week.
When your free week ends you’ll be given the option to sign up for Premium on a monthly or yearly basis. If you’re not interested, then you can just disregard. The ending of the free week does not charge you in any way. Enjoy your free week of Premium!