I have Usage Alerts set for each of our phones to turn off Data when the cap has been reached for that individual's Device. I also have it set that it will turn back on at the beginning of the next billing period.
BUT, under Device SETTINGS I *disabled* Data for one device thinking that Data would be disabled. Turns out that even though I have Data disabled, the data was turned on today because it was the beginning of the new billing period. I was told by online chat with customer service that I need to set the usage alert cap to "until I enable" instead. That doesn't make any sense; the Device Settings should supercede any other options.
I was by online customer service to post it here since "no one else has ever complained about this". So please upvote this if you think that Device Settings should take priority over Usage Alerts.