Hi David,
If the zone is already running, you will need to go to the home screen of the Netro app and press the square stop button to shut off the running zone.
If you want to cancel a future run, you can go to the Schedule page, select the day and skip the user programs. For Smart schedules, it does not make a lot of sense to skip a certain run because that will only push the run later in the day as the system is trying to maintain the moisture level. However, you can always skip all the schedules for that day.
Thanks,
Netro Support