There's a disclaimer on the speed both on the website and in the subscriber agreement, to the effect that speeds are not guaranteed. It pays to read those things so you can set appropriate expectations for a service you're paying so much money for.
The buffering can be caused by latency, Internet issues, and congestion (among other factors), not just speed. You can stream at slow speeds, actually, though this may vary by area.
If your installation was less than 6 months ago, your sales call may still be available. The HughesNet reps on this site can pull it and listen to it to see what the sales person told you and if they misled you. To have your call reviewed if it's still available, just start a new post and ask.
You can also begin a ticket here and try to get to the bottom of your buffering problems. You will have to run some tests and work with the HN agents on this site to try to optimise your system. If you only want to complain, you're in the wrong site. This is a tech support site, not social media.
"1.1 SPEED CLAIMS AND DISCLAIMERS.
HughesNet service is available in the contiguous U.S., Alaska and Puerto Rico. Stated speeds and uninterrupted use of service are not guaranteed. Actual speeds will likely be lower than the maximum speeds during peak hours. In addition, when connected to the Service using Wi-Fi, the user’s experience will vary based on the proximity to the Wi-Fi source and the strength of the signal, and its usage is subject to the Fair Access Policy."
The HughesNet website itself also has a similar disclaimer near the bottom of the page when viewing the plans available to you.