Adrian, I believe you helped spot the bug that may still exist in 9.3.1. My phone (or iPod, as Armen would suggest) was sitting beside my bed, updating apps. I'd clicked the "Update All" about 5 minutes before. WiFi Assist had been turned off and I suppose I was far enough away from the modem. Anyway, that's when AT&T started hitting me with automated text messages about my data plan being eaten up.
Anyway, since that disaster - and another one later that night, that mysteriously ate through another 500MBs sitting in the same place - my iPhone has since only chewed threw another 3MBs total.
This wasn't intended to be political - it did start out as a rant because I was literally shocked to have my phone chewing through data for some mysterious reason.
As to whether 300MB is a sufficient data plan, I'll know more in a month. I'm using the phone as I always do, and the rep at AT&T was kind enough to bump me to the 2GB plan for free due to the odd spike in usage. I doubt she's a software engineer, but some screen she had in front of her confirmed that my phone had eaten through a massive amount of data in a very short period of time.
But I think 300MB should be fine - as when I'm out, I don't spend my time with my phone stuck in my face. I rarely even touch my phone at home now, because all of my texts and phone calls are routed through my computer. And I can tell Siri to set alarms and do pretty much everything else I need the phone to do.
And today I'll put her through her most difficult test - as I'm attending a local festival. I've been to it numerous times, but my friends haven't, so the intent is to photograph and video a good deal of it to share. If anything out of the ordinary happens, which I'm sure it will, I'll put my phone down and enjoy the actual LIFE that is unfolding, rather than having a phone blocking my view.
I greatly dislike Facebook, I don't use Twitter, I don't need to stream music as I have 18GB on my phone, and I've had more than my fill of YouTube cat videos. I grew up without streaming tech and I can easily live without it, and I'm genuinely annoyed seeing people outside with their faces buried in their phones. It all seems very very sad.
So I'll report back as to how my iPod SE fares at the festival today. Normally my primary concern would be about the battery, but I suppose I'll be checking cellular burn intermittently.
As for people jumping to the defense of Apple or mocking people who don't use their iPhone to the extent they do - Apple does make mistakes. And I'd simply suggest spending less time on your phone and more time enjoying life. Though you might rack up tons of "likes" on Facebook over some silly photo, those are only from people who wish you to like their silly photos BACK, quid pro quo Hannibal Lecter style. Everyone else probably wishes you'd keep your tech photo album to yourself.
Now to go turn 4K video back to 1080p and make certain the option to share my photos to "the cloud" is most definitely turned off. I don't use the cloud properly either, as Apple wishes to charge me to share things with them I don't wish to share. And even in the event of a fire - I think the last thing I'd care about is my silly phone and photos no one else cares about - but nonetheless, I have a little firebox safe where I keep my TimeMachine backup. For whatever reason, I only had to pay once for both the safe and the drive. It's a very strange, sad iPod world I live in.
Thanks to most everyone for their help and advice.
And Adrian, if you happen to be able to replicate that bug, let me know. I hope Apple finds it and fixes it, despite those with limited cellular data being in the minority according to one person here who religiously monitors all such things here on the MacRumors forums, therefore leaving Apple with no reason to fix the bug
It most definitely bit me, so it exists - as perfect as Apple otherwise might be.
UPDATE: Adrian (or anyone else) - if you report bugs, it may be that once an update is initiated, cellular may be enabled to complete it if WiFi grows too weak or is lost? My best guesstimation. But the larger "bug" is not having ALL cellular burn "features" gathered together where you'd expect to find them, under "Cellular", and that - when turned off - they remain turned off. Hope everyone has a wonderful day!
I had an issue a few weeks ago where my phone suddenly went through 250MB of 4G data and prompted a warning that I was reaching my roaming package limit. I managed to work out what the issue was, and as far as I'm concerned it's a bug (and I reported it via the feedback app as I was on some 9.3 beta at the time).
My phone had many apps needing to be updated and they all started to update in parallel (I was on wifi at the time). It was crazy slow wifi so hardly anything downloaded. I have "wifi assist" turned off, but I believe that's only used in limited cases anyway and updating apps isn't one of them.
About half an hour later I went out. I checked just before leaving and all my app updates had not really download anything. It seems that, despite me having the app store disabled from using cellular data, as the downloads had all started they merrily continued to download, at lovely 4G speeds, as soon as I stepped out. Within a few minutes I got my provider-sent SMS telling me my roaming package was almost used and when I checked my updates they had all fully updated.