Locked out of Bellsouth.net email

I have a bellsouth.net email account I've been using for years in my business both on my phone and desktop. A couple years back, after a computer crash, I started using it just on my phone. Recently I upgraded to a new iPhone and all of myt settings were supposed to be carried over (like the past three upgrades). Well it appears most everything did EXCEPT my bellsouth.net email address. When I went back to the carrier they said they couldn't help me because the information was now gone. 

Here's the problem, I don't know my password. This account was set up by one of three of my accounting clerks years ago. I am not entriely sure when and by who. I have tried every password I can remember them setting up on things and nothing works. I have tried to recover it through the yahoo website to no avail.

This is an important business email address and I have years of important saved email including items important to a lawsuit I'm involved in. 

I understand the importance of difficulty in recovering passwords but I am desperate to do this. Each day I am missing important communications. There must be some way to speak to a human, give my SS#, DOB, Address, Phone#, whatever and convince someone that I am genuine.

Any advice would be greatly appreciated!