Data loss is most often caused by one of two things. The first is packet loss, which can be caused by a few different things, but most notably an incorrectly aimed dish. The second is something of the customer's using the data. Greater than 99% of the time it's the latter.
Many devices can use data when they are not being actively used by someone, and even when the devices are seemingly off. You can see the connected devices info, including devices currently connected to the HughesNet modem, and devices that have been connected, but have since been disconnected, here. It only shows what has been connected (and disconnected) since the last time the modem was plugged in, but it can be helpful in determining what may be using so much data. Notable culprits are satellite TV receivers, gaming consoles, and Amazon Firesticks updating background images. Devices getting into update failure loops can also cause high data usage. Devices that aren't getting a good WiFi signal can also use a lot more data than they normally would.
The following two threads may help you...
If you'd like help in determining what could be the cause of the problem, please start a new topic in Tech Support.