Your Member ID is the unique name you chose when you registered for AT&T service. It is the same as your email address. You can find your Member ID on your phone bill, in the Internet section. Your Member ID will look like this: firstname.lastname@example.org.
Your Member ID may end with any of these domains:
You cannot change a Member ID once it has been created. Forgot your password? If you have your Member ID, you can reset your password by going to: www.att.com/mybusiness. What is a Sub Account?
A Secondary Account (Sub Account) is an account set up under a primary account. For example, the account owner would have the primary account and their spouse or children could have secondary accounts. Each account will have its own User ID and password(s). The User ID for a secondary account will not appear on the bill. You may have up to 20 sub accounts (up to 10 active at one time) under your primary AT&T account.