With the latest iOS update, 15, there is a new option that allows you to let iCloud backups use your cellular data. Due to the amount of time these backups can take, it could cause you to quickly burn through your cellular data allotment. Even worse, this setting is enabled by default!
If you want to keep your iCloud Backups enabled, but avoid this possible risk, here is how to disable the setting over Cellular:
- Open your iPhone and go to Settings
- Select iCloud (click your name at the top), then iCloud -> iCloud Backup
- Refer to Back Up Over Cellular -> Set this to OFF by clicking the slider to the right