Why am I being charged for mobile data when I’m on WiFi?

[Emma340]

I have recently been notified that I’ve used 75% of my data; when I checked my usage several times I was at home connected to WiFi (and asleep) but have been charged for using mobile data - can anyone explain? 

[enlli]

I've never known usage figures to be wrong so you need to check your phone.

Most handsets allow you to view your usage on both WiFi and the network. As you say when you are asleep make sure your WiFi has not got a battery saving function where WiFi is turned off if the phone is idle for a period of time

Also make sure that ALL updates can only happen over wifi The same goes for the syncing of data (photos etc)

[Emma340]

Thank you, two follow up questions. I’ve been on the same plan for years and this is the first time it’s happened so I wondered if you might know what’s changed.

Updates etc are only done on WiFi already so not sure what else it might be.

I have an iPhone, where would I find the WiFi usage and whether there is a battery saving function?

Thanks again 

[pcg33kuk]

@emma340

Turn off WiFi Assist from the iPhones Mobile Data Settings.

As the iPhone will switch to Mobile Data, if your WiFi should drop.