One of my computers/allowed me to click on gear and “change back to Hotmail” of which i have no email record by search of automatic “upgrade” to outlook

I just completed training my staff on Hotmail use and do not want to "automatically " upgrade w/o time to plan retraining please restore my Hotmail capability asap If not I will contact Atty General, FCC, AZ corp Comm anyone required to get resolutuion