If you need to change a Two Factor Auth Users username then this can be done in two possible methods.
Method # 1
Delete the User account from the AuthAnvil Manager. This is done by Accessing the AuthAvil Manager https://(Your Domain)/AuthAnvil/Manager/Logon.aspx
Selecting Users, the specific Username. From here we select Actions - Delete user.
This will allow you to recreate the user with whatever username you feel they need.
We can also rename the User in the Anvil SQL DB. The advantage of this method is the user will not need to be re-assigned a SoftToken or reconfigured for SSO.
Step 1. Open SQL Management Studio, Databases, Anvil, Tables, dbo.Users.
Step 2. Right Click on dbo.Users and select Edit top 200 rows.
Step 3. You will now see a List of all your 2FA users and their UserID's.
Step 4. Select the Username field and make the necessary update then hit the "Enter" Key.
Note: If you do not have SQL Management Studio installed I would recommend using this version http://www.microsoft.com/en-ca/download/details.aspx?id=42299