In Planning, Global Schedulers, Editors, Admins, and Org Admins are set to receive email notifications any time someone accepts or declines an invitation to serve. To edit your notification settings, go to the Settings page and scroll down to Personal Settings. There, you can check/uncheck what notifications you'd like to receive.
The checkboxes under Email are for email notifications, while Mobile refers to push notifications if you have the Planning mobile app installed on your phone or tablet.
Note: You will only receive Accept/Decline notifications from other team members for services that you are also scheduled to serve on. For example, if you schedule out the Easter service but you yourself are not scheduled to serve in any role on that service, you will not receive notifications. Instead, if another Admin is scheduled on the service, they will receive those notifications so that they can be aware of who will be serving with them that day.
To workaround this, you could add an extra role for "Scheduler" or similar so that you can schedule yourself to all services and receive notifications without taking up an existing role.