Regarding the data usage issue, as you don’t recognize the hours and days with usage, we strongly recommend changing the Wi-Fi password as quickly as possible, as you may have a stranger accessing your network.
I see that you called yesterday to Customer Care and the agents recommended the same thing.
You can follow this guide: How do I change Wi-Fi settings on the Viasat Gateway modem?
Please let us know if you need any help changing the password. Again, as you don’t recognize the hours and devices and overall usage, we recommend making this change as fast as possible to avoid further usage of your network from strangers.