I caanot get a secure e-mail key for my main bellsouth.net e-mail

I cannot get an secure e-mail key for my main bellsouth.net e-mail.  For example, my email address is the first eight (8) letters of my last name.  However, AT&T thinks my main e-mail address has two additional characters in front of my email address.  For example, if my e-mail address were abcdefgh@bellsouth.net, AT&T thinks my main email address is xyabcdefgh.bellsouth.net.  HOWEVER, AT&T has the correct email address for contacting me about my telephone bill.

How do I resolve this problem?