Before they will consider cancelling they will want to work with you to try to resolve your issue. They will need you to run tests to diagnose the problem. I'm sure someone here will give you instructions.
*I am not a Hughesnet employee or representative. This is a customer-to-customer tech support community, and I am a customer.
Though it's a bit unusual for this to be happening, I would try disabling the WiFi in the HT2000W modem and then have someone call you on the cell phone to see if you're able to receive the call. Then re-enable the WiFi in the HT2000W modem and do the same. This would at least help to pinpoint the cause of the issue.
For instructions on disabling the WiFi, please see "How do I manage my built in WiFi?" in this PDF. Make sure that you disable each of the four radios individually rather than all at once, as unchecking SSID Enable for all four, then clicking Save Settings, may not save the settings. You should uncheck SSID Enable for the 2.4GHz radio, then click Save Settings, then do the same, individually, for the other three.
To be clear, you are saying your normal cell calls coming from the tower do not come in, not talking about cell over WiFi calls?
How many bars of cell signal strength do you have on your phone? Are you using some kind of cell amplifier/repeater?