Thanks for your post. Let’s try to diagnose your setup to find the issue here.
Could you please post one of the following - a recent case number, full name of the account holder, or serial number of your modem so that we may look into this?
Also, are you using a router? We suggest reading these threads first to see our progress in addressing these unidentified data usage concerns:
You may post your screenshots in this thread created for you so we can focus on addressing your concerns.