Mobile data

[#1]

Should I turn off mobile data when connected to WiFi or doesmy mobile use Wi-Fi automatically before mobile data

[#2]

It should use WiFi over mobile data but if your broadband connection goes down or there is a problem with your router then your device could switch to modile data without you knowing causing you to go over your limit as per this thread.

[#3]

You don't have to turn off mobile data. When you have Wi-Fi connected to your mobile you will see the Wi-Fi icon on top of your mobile screen. You can tell by mobile data or Wi-Fi is being used by the different icons. If you have Wi-Fi on mobile it will use Wi-Fi over mobile data. If Wi-Fi disconnects or you're out of Wi-Fi range then mobile data will automatically connect.

[#4]

And of course many phones have a variety of options like "use WiFi if available" and the catch all of "ask first".

[#5]

You can do, but I don't know your model of phone.

Yes I guess they'll have an icon to say I am using Wi-Fi and another to say 4G. Trouble is they will just switch without you noticing, and so it'll just carry on working.

I had this problem today when I was in town and I was by a Wi-Fi hotspot and it wouldn't connect. Detected it, wouldn't connect so I used 4G. Went somewhere else which worked, so I assume it was a broken hotspot.

Luckily I get 25Gb per month and I may use 2-3 at most - so I was more worried if there was some problem with the phone than using up my allowance.

My iPhone pulled this trick the other day where it would not connect to my router. A soft reboot fixed it and now it works. Didn't change anything on the router.

[#6]

Just to add to this, some smartphones have a feature called 'Wifi assist' whereby if a Wifi signal is being used, but is weak, the mobile data can be used to bolster the connection and speed things up. 

Confusingly, I think this will still display the 'Wifi' logo in the top corner, even if 4G and Wifi are being used in conjunction. We see this a lot with discrepancies in data usage, when a customer is sure they haven't used their data as they use Wifi at home, but the smartphone has been using both at the same time.

A quick check in the settings menu to make sure this is switched off is a good idea

[#7]

On Android there is the abililty to stop applications using mobile data when running in the background. This is under settings, data usage and can be set on a per application basis. If you leave mobile data on all the time, it's a good idea to check what each app is using and then maybe use the above setting to disable those you don't need to use data in the background.

[#8]

When you're at home, your phone will connect to your wifi, and use that instead. However, you will often find that, when you are out and about, your phone will try and use a wifi hotspot, but you have no actualy internet connectivity: what's happening there is that whilst you have connected to the wifi ok, you need to log in to that wifi before you can use it (which is why you don't have any actual internet connectivity!)

When I'm out and about, I often find that I have to turn off my phone's wifi, so that it will use the 4G instead: Yes, if you are static, I could just log in to the wifi, but usually I'm walking about, so it's not a good option.

Typically, if a phone has connected to Wifi, but NOT to the internet, then your wifi icon will have a "!" next to it.

[#9]

I rarely turn mobile data off, I just leave it on and use a hotspot if one is available.

Thing is on my plan I get 25Gb of data per month, which is more than enough for me. I may only use 2-3Gb's of that. I sometimes just use mobile data anyway, but there are no hotspots such as the overground when I am travelling to and from Central London.

Even then if a hotspot is available I find 4G faster than the speed they provide.

For the OP, unless you using more data than you thought you would be, and you're using up most of your data allowance I wouldn't worry personally.