■ Why did the remaining balance run out so quickly?

Checkpoints to confirm (iOS): 

1. Automatic app updates have occurred 

Automatic app updates can consume a significant amount of data. 

To mitigate this, go to "Settings" on the home screen, then "General," and set "Background App Refresh" to "Off" or "Wi-Fi." 

2. If "System Services" are consuming a lot of data 

Tap on it for more details. Sometimes, "Software Update" can use a lot of data. 

In this case, go to "Settings" on the home screen, then "General," and turn off automatic software updates under "Software Update." 

3. Identify and close data-consuming apps 

Running other apps in the background can lead to excessive data usage. 

Go to "Settings" on the home screen, then "Cellular." 

Scroll down to find "Roaming" and "Total" data usage. 

Here, you can review data usage for each app. 
 

Identify apps that are consuming a lot of data and set them to "Off." 

They are listed in order of highest data consumption. 

Please note that this usage data only pertains to the apps; the system's usage is not included here. Names for the connection type (e.g., "Travel," "Work," "Personal," "Mobile Data") may vary based on your settings. 

4. Check your iCloud settings 

Go to "Settings" -> "Cellular." Scroll to the bottom and turn off iCloud Drive.