The Civica Scheduling mobile app uses a small amount of data to get your list of visits and to check-in/out. It will use more if you send photos back.
The data usage should be relatively low, but if you're concerned, here's how you can check how much data had been used:
Steps may vary slightly depending on the device: go to Settings > Data Usage > Find Civica Scheduling. You can also restrict the data to only be sent and received via WiFi connection by ticking "Restrict Background Data".
To view the cellular data usage for your apps, tap Settings > Mobile Data (sometimes called Cellular). You can turn cellular data on or off for each app.