Yes, AT&T does have service outages and (maddeningly to me) degrades service during upgrades. I don't like being told "we're upgrading the network to give you better service" when I have a C-level executive complaining.
With that said, AT&T customer service treats one report of an issue as your problem. If you give them two or more phone numbers they take a more introspective look after covering the basics. I won't call support if I can't reproduce it on another phone... I don't think they take a one phone support call seriously.