I'm not sure, but I don't think it's a violation of the EULA to use 2016. As far as I know, the subscription model is based on the number of users in your office, not necessarily which versions are being used. So you could have 10 people in the office, and every person could be running a different version. As long as you're paying for the seats I don't think Autodesk cares which versions are being used. I could be wrong, but that's how I understand it.
Funny story: There was a guy at the last office where I worked and he always refused to upgrade. He liked his old version, (can't remember which one), but one day they finally convinced him to upgrade. He wasn't happy about it though and he kept the old version installed and continued using it locally, saving to his computer. He would work in the old version all day, and when he was done, he would open the drawing in the new version and save to the server. The only thing he used the new version for was saving. I wonder if he's still doing that?
Using the educational version for commercial use is a different story though. That's definitely a clear violation. And since they keep stiffing you on payment for the work you do, maybe an email to Autodesk might be in order?