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I'm on holiday in France with my 100 GB pay monthly Vodafone plan, but get virtually no data when roaming on either SFR or Orange. Every now and then WhatsApp messages and sometimes email drip through but it's impossible to load a Web page or use an app. I am having to ask my partner to share her Three PAYG internet via a mobile hot-spot if I need to use the Internet. Three works like a charm in the exact same locations however Vodafone is an utter disaster. What's going on? The problem is NOT the local network as both SFR and Orange have excellent coverage and speeds in the urban locations where I have been. The problem is Vodafone!
You shouldn't have any problems with SFR, they are a good network but Vodafone has no control over a roaming networks outgoing roaming traffic management.
Try refreshing your SIM by doing a network scan and reselect the roaming network, this may help.
If you still have issues this could be account related and you will need to contact Vodafone to make sure there are no restrictions on +447836191191 or speak to the Social Team here: Contact Us
There is also a cap across all account for 25GB monthly roaming data.
Check the relevant networks masts to see if an issue is known @Jonasp
In the interim I can only suggest using Wi-Fi where it's available and if your phone is unlocked to all Network's use a local sim card.
I know you shouldn't have to but sometimes needs must.
I hope this sorts itself out for you.
Current Phone >
Samsung Z Fold³ 5G.
Previous Phone >
Samsung Note 20 Ultra 5G - SM9860.