Pretended to be AT&T and caller ID showed "AT&T SVC CTR". Caller had issues maintaining a professional aura and gave me a generic Mexican name "Hosé Lopez". No hint of ethnicity in his accent.

Did not ask for DoB (and maybe a security question) which is what AT&T requires before talking about a subscriber's account.

Offered an "internet upgrade for DSL". I stupidly said "Oh, U-verse upgrade huh?", and of course he led me on. He made up some numbers for the speed and did not understand the difference between download and upload rates. He was at a loss.

Called the number back from a different number. Straight to the holding queue, music playing, no identification message.

They aren't even trying.

man called...very unclear last name, "antonio sanford"  (?)  kept asking for my date of birth.  said he was from att.  said he wanted to give us a free upgrade- never clear on why att had him call me.

No answer

Call from this number claimed to be a collection agency calling for Sears and were completely unaware of the $25 a month payments being made on the account as set up by a judge and the court.

I've gotten calls from AT&T from various other Toll-Free numbers, and a few times from a number with a Texas area code.  I never answer it.  Not only do I not want to talk to AT&T, it could be someone posing as AT&T in a phishing scam.  Fortunately, I've only gotten one call from his number & no message, not even a recording.

Since I've recently changed my services, the calls have increased.  The Caller ID just said "Toll Free Call."  

Next time I need to talk to AT&T, I'll ask for the number to call to be placed on a Do Not Call List.  I won't trust the number displayed.

AT&T service center.  Call them back and press 9 to be placed on the do-not-call list.

UPDATE: I called the number and the recording that answers identifies it as an AT&T Service Center. I didn't wait to speak to anybody, as I'm assuming it's a call asking me to sign up for something.

The caller left no message