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I'm roaming in autralia where vodafone.au coverage is as bad as in the UK. If the faintest of voadone reception is available I can only connect to that not the better Optus or Telstra. Occasionaly I get onto optus, but everytime with Tesltra I can the message "your sim card does not allow a connection to this network"
So my partner roaming with EE is able to stream using 4G, whilst I cant even make a clear phone call.
It is just another reason why I cant wait until contract renewal time. I need to use this phone for work
Your phone would auto connect to the network Vodafone partners with and if you choose to manually connect to another network in your phones settings if that's not holding then there isn't much you can do with that unfortunately @tuckleyn
The alternative if your phone is unlocked to all networks would be to use a local sim card or another UK Networks sim card that allows you to latch to the best network or use wifi.
Current Phone > Samsung Note 10+ 5G _256Gb > Model: SM-N976B.
Samsung One Ui / Pie.
Samsung Gear s3 Frontier Watch.