Help Why does my Pixel 3A go online when I don't want it to?

I have a Pixel 2 rather than a 3A, but unless it's a feature added since November we likely have the same options. However I always leave mobile data on, as I suspect most do, so I can only speculate about this problem.

One thought: when I turn data off there is an option appears to allow me to send/receive MMS (which uses data, though with my provider that's on a different APN). Is it conceivable this is what you are seeing?

Another is whether you have any app installed that could override such settings? This is a tricky one to pin down, since the permission CHANGE_NETWORK_STATE, which I think is the relevant one, is not as rare as you might hope: if I look through apps on my device that have this I can see why some need it (e.g. Tasker, or the app I use to connect my camera to my phone), but damned if I can think of a reason why so many message apps would want or need it, or ******* Facebook of all things. Of course having such a permission doesn't mean that an app is abusing it, it just makes it harder to track down the culprit if there are many candidates.

You could try running in safe mode for a while and seeing whether the problem goes away (of course how long it will take to tell will depend on how common it is). If that stops it you will know that it's an app you have installed, and it becomes a matter if tracing the culprit. If not, then you know it's something pre-installed.

The only other thing I can think of is to look at your app data usage and see whether you can spot which apps are using mobile data. Of course if the connection is turned on then many apps will, but if it is an app that's turning it on you might guess it would appear on that list, so I'd be tempted to look at that list and then check the permissions of those apps.

Unfortunately Google do not consider this type of thing a sensitive permission, and so do not allow you to deny it to an app. So if you do manage to identify a culprit (assuming that it is an app in the first place) your only option will be to remove the app.

The email thing is very odd, since something would have to tell the phone that an email had arrived in order to turn the internet connection on, which of course requires an internet connection...

MMS are different: the network will use the SMS protocol (which doesn't require a data connection) to inform the phone that there is a message. But email is very strange: sufficiently so that I've just turned WiFi and data off and sent a mail to my GMail account (as I reckon that's the one with the most obvious connection to Android or Google). So far nothing has arrived and the phone remains disconnected (about 10 minutes now). What email app do you use? I'm thinking that if anything will have a back channel it will be Google's apps, but I don't use the GMail app myself (and in fact have it disabled).

This looks like a job for a Firewall!

https://noroot-firewall.en.uptodown.com/android

https://f-droid.org/en/packages/eu.faircode.netguard/

Another thing to to is to look at what apps are able to use data in the background, and turn that off.

Try using your 'data saver'.
It is supposed to allow data connection omly for apps that you are using at the moment.
This probably means that you would also need to get them out of recents when you are done with them.

Try opening your developer options, and scroll to near the bottom.
There you should find 'background processes'.
I usually have my good devices set at three or four, my crappy devices at none.

Mostly I use this just to keep Google Play Services from running endlessly in the background, at least on the devices that still have that horrid thing enabled.

JimmyPixel3a said:

@puppykickr , thanks for the suggestions.

So I can confirm one of the reasons why my Internet Connection is kicking back in and using my data is when someone sends me an MMS, I go back online. Found that out the hard way when I got back home tonight. Strange thing is I changed the "Messages" app to not use data in the background.

Click to expand...

Yeah, that is odd.
As far as I know, a data connection is not required for texting.
Not too sure about MMS, though.
Because of the file sizes, it could very well be different.

A firewall could be used to end this issue.

If you are not real familiar with one, I would try NoRoot, because it is extremely simple and effective.

puppykickr said:

Yeah, that is odd.
As far as I know, a data connection is not required for texting.
Not too sure about MMS, though.
Because of the file sizes, it could very well be different.

Click to expand...

MMS does require mobile data, unlike SMS, but you'd expect it to limit the connection to just downloading/uploading the MMS.

Many carriers use a separate APN for MMS, which keeps MMS traffic and connectivity separate from general internet usage. It would be interesting to know whether you have this or not - that might be relevant to this unexpected behaviour.

(Personally it's been years since I've either sent or received an MMS. Here in the UK SMS have been effectively free for a long time, but many carriers charge exorbitant amounts per MMS, despite the poor image quality. Hence the various internet-based chat apps have completely replaced MMS over here.).

Yes, but unless the code is stupid I'd not expect that to turn data on for anything other than MMS (i.e. not leave it on afterwards). This is why I wondered about whether you had one APN (for all mobile data) or two (one for general data and a second one specifically for MMS). "APN"s are "access point names", which you can find in the mobile data settings.

Well, from what I see here, it appears that you need to turn that switch off (send and receive when mobile data is off) and see if this issue still occurs.

My guess is that this is a sneeky way to keep turning your mobile data on and leaving it on without really telling you that this is what they are doing.

Sounds like something right out of the Google playbook.

JimmyPixel3a said:

It looks like I only have 1 APN although I see 2 options (Mobile Internet and Tethered Mobile Internet). The one that's selected is "Mobile Internet".

Click to expand...

Yeah, so that suggests your carrier uses the same APN for MMS and general data usage. I don't know whether that's relevant, but it's easier to imagine a bad implementation allowing the data connection to be left open for other traffic (as opposed to only allowing one specific service to use it) if it's all using the same APN.