How to verify AT&T caller?

I just had a call from someone supposedly from AT&T. He wanted to know about my service, said they were discontinuing copper, thought I had 2 lines (I don't) and if my bill had increased in the past two months (it hasn't) and if it was still under $100 (it is). This seemed like too many errors and unknowns for someone who had access to my account information, so I asked who he really worked for. He gave a name, saying they managed the accounts. I said they were not managing them very well if he didn't know the details about my service. I told him I had resolved a noisy line problem with an AT&T technician last week. He noted that (wasn't aware of it), said thanks, and hung up.

How can I check to see if this is legitimate? The AT&T website provides no human contacts.