If you want to cancel your Premium subscription, please keep in mind this is only possible once the locking period of 12 months has ended and has to be done manually.
You will just need to go to the Profile section in the SwissBorg app and tap on your Premium Plan just below your name and account creation date.
This screen will show you all available plans and their benefits, and how the different Premium Plans compare to each other. If you tap on your current plan, the next screen will show you the amount of locked tokens and whether the 12-month lockup period has been completed yet.
If the 12 months have passed you will find at the bottom of the screen, in red, the "Cancel Premium" button.
If you cancel your Premium plan and later would like to become Premium member again, you'll have to lock your BORG tokens again for the minimum locking period of 12 months.