There is the case that a user in one company will need to be switched to another that you have in Planhat. Luckily, it is super quick and easy to do and you don't lose any of the data attached to that user.
All you have to do is go to their user profile and edit the company name under their name.
And voila! It has been changed to the new company and the entire history of the user is still in Planhat.