Bellsouth.net is similar to your sbcglobal.

So this is how I manage them. I have two accounts that are connected with yahoo. One is an actual yahoo.com. For that one I make sure the site url I am on IS www.yahoo.com. Then sign out if it is signed in. When you sign in if I type the bellsouth account and click sign in it takes me to a different site to sign in and works fine, assuming I have the right credentials.

If I want to use the other yahoo account I have to first sign out of the first, navigate back to www.yahoo.com and make sure to use the right email addy when signing in.

It always sign out and sign in to switch from one to the other. I just tested and I can log in on both. I don’t know if this helps you. But the issue I have is when these accounts conflict in the browser.