Hi there, this is the easiest way to take care of this issue:
One thing to make sure of before proceeding with the steps below, is if they have any Presentations or Storage files in the account they are logging into incorrectly, they should retrieve it before proceeding. Let us know if you need any help with that.
1 - Have that user log into https://apps.risevision.com using the account they created.
2 - Once logged in, ask them to click on their Company name in the top right, and select User Settings.
3 - Click on the Delete button, and confirm the deletion.
4 - Now that they have been deleted from that Company, you can add them to the correct one.
The next time they login, they will log into the correct Company.
I've gone ahead and taken care of this for you. Please see the email followup.