iPhone network issues

[Mollie3]

Not sure if this is an iPhone issue or an issue with o2 network.
The last couple of days my phone won’t connect to any WiFi (although it says it’s connected it still says 4G in the corner of phone)
My phone is saying I’ve got 4G but the only time this works is in safari, none of my apps will connect to the internet meaning I can barely use my phone.
I’ve reset all my network settings but nothings changed.
Any ideas?

[Bambino]

@Mollie3 You can check if there's a network issue here: O2 | Service Status

Your WiFi has nothing to do with the O2 network. If you're having a problem, go into your settings and forget the WiFi router, then re-enter the details and reboot your phone and router to see if that helps.

[MI5]

@Mollie3 

Check in Settings >Mobile data and scroll down to see if the apps listed are allowed to use mobile data.

You need to set the switch to green for each app.