ATT used to have a webform to use to request delisting. I’ve heard reports over the last few months that the form isn’t working. This week, the website hosting the form disappeared. I don’t know for sure, but this looks like this is either deliberate or there’s just no one in charge of the site and it got lost. ATT provides an email address for delisting, too...
June 29, 2017
Delisting at ATT