All Virgin Mobile SIMs are compatible with 5G
So if you've had the text to say the SIM has moved radio networks, and you've got the latest iOS Carrier update, then you should be good to go for 5G when you're in range of it, and now also VoLTE. WiFi Calling will continue to work if you're already using that.
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I work for Virgin Media - but all opinions posted here are my own