SafariOffice allows Admins to manage and cancel optional Add-ons (such as Multi-Language, SafariBuddy App, or Share Tours Add-ons) directly through the settings.
Go to your subscriptions: Setting > Subscription & User Accounts > Subscriptions
For the Add-on you want to cancel click the three green dots at the end of the line.

Click 'Cancel subscription'
In the window that opens click 'Yes, cancel subscription' to confirm.
The subscription will be canceled from the next renewal date, you will keep access to the Add-on until that date.