This tutorial will show you how to restrict your users from changing their username. Go to Administration from the main menu and select Campus Settings from the drop-down options.
In the Account Details, click on Customize and scroll down until you see the option that reads, Disable username changes. Check that box and scroll down to the bottom of the page and click Update Account to save your changes.
If you need further assistance on this topic, feel free to contact our support team anytime between the hours of 8am-5pm, Monday thru Friday, or if you prefer emails to phones, submit a support ticket.