Cut off from our email

We are at wit's end. Customer support says they can't help.

We have been using the original email address we got well over a decade ago from PacBell. PacBell got incorporated subsequently into ATT, but they said we could keep our original email everyone knew.

We've used Thunderbird to access ATT's servers to use our email. We've had the same password for ages.

Suddenly last week, it wouldn't connect. We tried repeatedly through Thunderbird but it and the ATT.com website wouldn't connect. 

I called customer support. Over the course of over a week, they talked about things like our account becoming unsynched and that they'd fix it soon. Eventually, many calls later, a supervisor said that unsynching had nothing to do with it. The account profile needed more information (we never knew this.) Trying repeatedly to access it with our password resulted in a fraud lock. They would normally just reset the password. But because profile information was missing, they couldn't. They told us there's nothing anybody can do. 

Meanwhile, nobody sending us things knows the emails aren't received. This is a business email, the results could be a disaster.

Is there anybody with suggestions as to what can be done or who could do it?

I called the retention department. They said to call web.com or something or use the "contact the president" option on ATT's website. The web.com people had no idea why we called them about a pacbell account. I see no "contact the President" option here, I can keep looking, but I thought I'd try this first.