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Just switched to Vodafone as they provided better coverage than my last network. However my phone (Apple iPhone 7) says I'm connected to 3/4G but when I go to use the internet or anything else requiring Wifi, I've apparently got no internet connection.
In terms of accessing the internet over the mobile network it might be worth checking your settings. There's a guide explaining how to do this, here.
With regards to wifi, this wouldn't be related to the mobile network and could be down to the router or access point you're trying to connect to. Are you able to connect other devices to the same wifi?
Vodafone customer since 2004. Attempting to help where I can on the Community
Exactly the same happened to me mate. Turned out the port was just a bit delayed, after another day my data started working..,
Once my number switched over everything was working. However I have signal in my flat but my 3/4G still isn't working despite saying I'm connected. Only happens in the flat.