Xbox Game Pass Ultimate isn't yet available to everyone, but it will be at some point later in 2019. Right now, select Xbox Insiders, those in the Alpha and Skip Ahead rings specifically, are able to try it out at a reduced rate and provide Microsoft with valuable feedback. However, you can cancel it at any time and the method for doing so will be the same when it rolls out to the public.
Full story from the WindowsCentral blog...
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