First - update to the latest version of the Lüm app! Second - enjoy some awesome new features!
We heard your feedback from the Member Forum and released a number of new features on August 10th (all at no extra cost to you). Learn more at https://help.lum.ca/kb/articles/65
Managing data usage
There are many apps, settings, updates, including backups that can use up your cellular data (in the background) and thus escalate data usage while not connected to wifi . My home wifi can handle most of these tasks generally and for the most part it does. There are YouTube videos that can help people manage cellular data usage/ turn off settings etc.
I personally switched off my data to start with , because I have good wifi at home. I do use it , but only when I need it. In addition, I found a video helpful change some settings: one example for iPhone https://youtu.be/_bK9eWegVng