If Windows is updating without permission in one of your companies, there's an issue with whoever manages IT for that company. Even without an Enterprise license, it's trivial for a domain environment to control update behavior. Group policy handles the majority of these concerns easily.

Even if you could install Windows 7, you would be very mistaken in doing so, as it would put your company at significantly greater risk. Even while security updates are still available, the differences in the platform already lead to scenarios where large malware infections tend to be almost entirely on machines which weren't running Windows 10.