have you tried doing a manual network search in the phone's settings?
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Welcome to the community
Sorry to hear about the roaming issues you're experiencing at the moment.
Could you just double check that the roaming is fully activated on your account for me?
Just login to your online account here and click on 'Plan and device' and then 'Manage services'.
Check that the 'Going Abroad' option is set to 'On' and also that the 'International Call Baring' is set to 'off'.
Let us know how you get on.
Mark YForum Team
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