Sudden increase in data usage on iPhone 7

@MCll22 If you look in the settings of the phone (under cellular) you can see which apps are using the most data.

If you haven't been resetting monthly, it'll be a large block of data, but if you reset and it keeps using data, you'll easily see which apps is using the data.

Please know your data isn't reported live, data can be reported up to 72 hours late, so just because you are ON WiFi and see data being used at the AT&T site it doesn't mean you are using data then. The meters on the phone will be accurate as to when it is actually being used (it's reported immediately).

At the bottom of your Cellular settings is the Wi-Fi assist option.

If it's switched on, your phone will start using cellular data when your WiFi signal becomes weak.

Switch it off, and you'll get all your data across your WiFi network, as long as you're connected to it.

Adriaan

@MCll22 Did you ever figure out what was causing the issue?

@ameijer wrote:
I believe it was the "Wi-Fi assist" option at the bottom of Cellular settings. With it on, I started using cellular data when in a room of the house with a weaker WiFi signal.

You believe? How much data did "Wi-Fi assist" say it used, it should have had a specific number there.

If my AT&T data usage on their website is accurate, I went down from roughly 100 MB per day to less than 10 MB in three days.

That's a pretty small data sample size to come up with any conclusions.

Data can be reported up to 3 days late at AT&T, so that's even more questionable.

@at&t have you seen a rise in this situation? I have an iPhone 6 and iPhone 7 and the 7 literally uses 4 times as much data with similar settings and usage. I have already been through the settings, cellular, WiFi assist, app update times etc. I have concluded it must be the phone, which also seems illogical but is the only thing I see different between the two. 

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@Elsee530 wrote:

@AT&t have you seen a rise in this situation? I have an iPhone 6 and iPhone 7 and the 7 literally uses 4 times as much data with similar settings and usage. I have already been through the settings, cellular, WiFi assist, app update times etc. I have concluded it must be the phone, which also seems illogical but is the only thing I see different between the two. 

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If you look in the iPhone settings, under cellular it will tell you EXACTLY what the phone has used.  The only issue is that it doesn't reset itself monthly, you need to manually do that your self.

But you should easily be able to see which apps / processes are eating the most the data up.

It can absolutely be the phone.  One thing you can do is remove the SIM card and see if you have Wifi access or not.