Welcome to Vodafone Community
Hey @hilarythacker I hope you're doing good 😊 I know how important it is to be able to stay connected when you're out and about so let's get this sorted for you 🙂 If you've recently joined us you may need to update some settings on your phone to ensure your 4G stays active.
If you are using an android device, text WEB to 40127 and you’ll receive a message that will help you make sure your settings are correct.
If you are using an Apple device go to Settings - Mobile Data - Mobile Data Network and make sure every single APN (Even the one in the LTE setup box) say wap.vodafone.co.uk and all of the usernames and passwords say wap
You can also find step by step guides on how to set up your phone for data use here
Once you've updated your settings, restart your phone and see if you can use your 4G data when the Wi-Fi is switched off!
Please do let us know how you get on.