How do I unmerge my Yahoo email w/my SBC/ATT email? My SBC/ATT dsl has been cancelled since Oct 2006.

I cancelled my SBC/ATT dsl Oct 2006 because we moved. I was able to unmerge the main email address but I was not able to unmerge 3 of the 4 subaccounts. I get message with an unmerge on but when I press it, it says to try later. I tried to call SBC/ATT but they were incompetent & unable to help. After several calls they finally said I had to wait 6 months & the emails will automatically unmerge. I've tried to make a new email address with the same name but it says it's already taken. I've called ATT back several times thinking I will finally get someone who can help but still no progress. It's almost 2 years now. But my kids keep wanting to see if they can reinstate their yahoo accounts. Can anyone help??