48 don't support 4G at all.
They support "3G" up to H/H+.
https://www.quora.com/What-is-the-difference-between-E-H-H+-3G-4G
EU roaming calls, texts and data work on Guido and not on any other membership.
But some people still have problems even when these should work.
Are you abroad now?
Are you having problems?
Or are you just asking in advance of travelling?
Hope this helps.
Did that help at all @alice1947 ?
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