Why does mobile data usage increase when not in use?

Mobile data usage oftenincrease even when you're not actively using your phone, and there are a few reasons why this might happen:

Background Apps: Some apps on your phone may continue to use data in the background, even when you're not actively using them. For example, social media apps may periodically update to check for new notifications or messages, and some apps may automatically download updates or content.

Operating System Updates: Your phone's operating system may periodically download updates in the background, even if you haven't explicitly requested them. These updates can be large and can consume significant amounts of mobile data.

Automatic Syncing: Some phones automatically sync data with cloud services, such as photos or contacts, which can consume data even when you're not using your phone.

Malware: In rare cases, your phone may be infected with malware that is consuming data without your knowledge. If you suspect this may be the case, it's important to run a malware scan on your device.

To reduce mobile data usage when you're not actively using your phone, you can try the following:

✓ Turn off AUTO SYNC & background data for specific apps that you don't need to update in real-time. 

Here is the path how you can Turn off AUTO SYNC on your smartphone showing on below pic.

✓ Adjust your phone's automatic update settings so that updates only occur when connected to Wi-Fi.

✓ Limit automatic syncing of data with cloud services.

✓ Monitor your phone's data usage regularly to identify any unusual spikes in usage that may indicate malware or other issues.