Thank you for your post, we want to address your concerns. Please post a case number or the serial number located on the bottom of your modem so we may look up your account.
Please follow these initial troubleshooting steps and post back with the requested screenshots:
Keep in mind there are countless factors that can use your data, since you mentioned you use Norton 360, please pay close attention to the point about automatic updates:
- more devices are capable of connecting to the internet: phones, tablets, gaming consoles, SmartTVs, and even refrigerators can connect wirelessly to the internet. Keep track of what devices you leave running on Wi-Fi.
- automatic-updates: your computer and any other programs you use will often keep working in the background, even if you're not actively using that program, in order to keep your system/program up-to-date. Anti-virus programs will periodically use your internet connection to check back with their malware database for any updates. You should have an option to turn off auto-updates and/or schedule them for a later time.