For Divisions that do not have a game schedule created, you can drag and drop Teams from one Division to another, keeping their rosters and any practice schedule intact.
How to move a team to another Division:
Go to Schedules > Leagues & Divisions.
For desired League, click the double arrow icon to Reposition Teams
On the Reposition Teams page, expand the desired division by clicking the arrow next to the Division’s name.
Drag the Team from one Division to another.
For instructions on how to move a Team to a different Division once the schedule has started, click here.