If your services are removing a time from the schedule, you can reflect that in Check-Ins by removing a time. As long as you're on a new session, the previous attendance will be kept, and your new times will show in the future.
From the Times tab, choose the service time you need to remove, and then click Delete.
If your event isn't set to recur, you can click Start a new session from the top right of the event.
From the event, click the arrow to go to the newest session.
Since no one has checked in to this time yet, no attendance information will be removed. That time will remain for past sessions, which means the deleted time will continue to show on attendance reports that include those past sessions. The deleted time will also be listed as an option in People list conditions.
If you forgot to remove a time before people started checking in, you need to edit the check-in to the time you are keeping.
Filter to the check-ins that belong to the time you want to delete, and then click the first check in.
Check the time you want to keep, and then uncheck the time you plan to delete.
Click Next, and then follow the same steps until all the check-ins to that time are removed.