Can't get into my account

I recently transferred the main line on my account to another provider. And now I am unable to access the account any longer. My email address was attached to the account, but that does not work as a log in.

How do I access the account? If I set up an ID with another one of the numbers that is on the account will it let me make changes to the account? I was under the assumption that I would still be able to manage all of the other lines on the account.