Why does the 877.285.***. act and sound like a phishing scam ?

Does anyone else think that the 877.285.***. message saying that your account has a temporary protection lock looks like a phishing attempt ?  And then that the 877.285.***. number, when called, sounds even more like a phishing boiler-room ?  
 
I got the following message when I tried to sign in to myATT account :- 
 

Screenprint converted to jpg ... 

The colours don't look like AT&T.  I checked online, and found posts that said it was a scam as well as posts that said that it was a legitimate AT&T-associated number. 

After giving it some thought, I went ahead and called the number - 877.285.*** - and, when it was answered, it didn't have the customary (and yes, the annoying, but I am willing to put up with the annoyance for AT&T's usual good service) AT&T tones and canned message(s) in the now-unavoidable AT&T voice system.  It sounded like a noisy boiler-room.  The person who responded had a heavy non-American accent, which can be quite common nowadays, and that wasn't a concern.  Him asking for my passcode before he was willing to tell me what the problem was - *that* was a problem.  For all that I could tell, the person couldn't access my account using my name and phone number enough to tell me if I had an actual problem or not, and he kept saying that he had to be given my passcode.  So I asked for a supervisor (this was 10 minutes, already, into the call).  
 
Ten further minutes later, another voice came on, introduced himself as a manager, and asked for a passcode without being able to tell me if I even had a problem or not.  Since this second person also had the excessively-noisy boiler-room background noise, and since I didn't get any better information from him, I thanked him, and hung up. 
 
Further online research suggested that I should use 611 to call AT&T - which should be harder to fake or spoof or intercept - so I called 611 ... and as soon as it answered, I heard the classic AT&T tomes, followed by the acceptably-annoying AT&T voice system, and I followed the prompts until I got through to an actual human.  This human, who was very polite and helpful, had some minimal background conversational noise, at the level I associate with cubicles, not a boiler-room.  She asked for my details, and then my passcode, which I gave since the rest of the interaction prior to her had the sounds I associated with AT&T.  She was then able to tell me why there was a temporary lock on my account, and she got me to the appropriate person in the Fraud Department (after appropriate AT&T sounds) who was able to straighten things out quite promptly.   
 
I am posting this here so that anyone else having a similar experience to mine can try this solution which worked for me (including *why* it worked for me).  The AT&T-associated noises are the auditory equivalent of the visual background in an AT&T store - they give we mere mortal customers the reassurance that we are dealing with actual AT&T support.  
 
If an AT&T Moderator reviews this question/post, it can perhaps be sent up the line through management to be considered as a suggestion supported by reasoning, too. 
 
I thank the AT&T personnel who helped me to resolve my problem.  They were courteous and patient, and answered my questions, even as they resolved my problem.  They were a credit to AT&T.
 

[Edited to comply with Guidelines]