What are the filetypes (extensions) of those attachments? It's much better to SEE that it is .pdf than to ASSUME that it is .pdf.
Since we can't see that mail, nor change the settings on your PC to show the extension (if currently set to hide it, a foolish Microsoft default) you're the only one around that can answer that question. We can't and AT&T customer service can't.
So it's quite unclear why you asked them and us in stead of just looking. Much easier, much faster, more reliable and certainly less frustating and scary.
The email AT&T "customer service" sent me -supposedly confirming contract changes discussed by phone - arrived with only 1 of the many changes specified. But the email had an attachment and instructions [DOWNLOAD ATTACHMENT] which I foolishly assumed carried a pdf with more details. One of the 2 (visible) downloaded files opened with omni outliner.
During my second call to "customer service" i asked what the attachment was - and was told they are unaware the emails contained attachments. This was only one of a series of frustrating and scary denials of knowledge, responsibility, or accountability but it is the scariest. What did i download onto my computer?
IS IT A TRACKING WORM MAL SOMETHING?? bin?