Hi @Steven_L
Thought I'd jump on this thread as I'm having the same problems as OP, let me know if I need to start a new one. I have no options for 5G in my network settings. I have tried turning the phone off, removing the sim and restarting to no avail.
I'm using an unlocked OnePlus 8 with a pay monthly SIM. I've had 5g coverage before with a previous network, but nothing since joining Virgin.
Will I require a new SIM as well?
Thanks in advance