The choices 'Consumer User' and 'User' are not visible when the 'Class' field value is set to 'Contact' on the 'sys_user' table.

The choices 'Consumer User' and 'User' are not visible when the 'Class' field value is set to 'Contact' on the 'sys_user' table.

When a user is created as a "Contact", it cannot be changed back to "User".

• Login to any London or Madrid Instances
• Navigate to plugins and install 'Customer Service' plugin.
• Open any record from the 'sys_user' table
• Configure form layout and add the 'Class' field to the form.
• Change the value of the 'Class' field from 'User' to 'Contact' and save the form. 

Issue: Please note the other choices (User and Consumer User) are not available after changing the value of the class field to 'Contact'

The problem has been closed as "Working as Expected" with the below reason:
"Because of the way table per class works, we can not go back to the parent class out of concerns for data loss. Switching to utilize table per hierarchy would allow the desired behaviour but may have other issues". Below is the link to the documentation that explains the same with additional details:
https://docs.servicenow.com/csh?topicname=c_TaskTableFlattening.html&version=latest

Choices for 'Class' field are populated based on table and extended tables. 'Customer Service' plugin has two tables extending 'sys_user' table.
When a record class name is changed to child table, the record is moved to child table and moving it back to parent table is not possible.

Instead of changing the class name of a user record, customers need to follow the recommended way while creating customer contact or consumer users https://docs.servicenow.com/csh?topicname=c_ManageUsersFromCustomerPortal.html&version=latest