This is how you switch to myClubs UNLIMITED:
Open your profile in the myClubs app
Click on "Membership" > "Change plan"
Select myClubs UNLIMITED
Your membership will always be changed at the start of your next booking period. You cannot change your plan during the current booking period. The next possible date for a change is therefore already preselected in the app. All you have to do is decide which sports subscription you want to train with afterwards and save the settings.