I'm experiencing the same issue as well. Updated to 11.2.5 and still no iMessage activation possible. I also had the issue of sending messages to my wife on Friday (also on Virgin Mobile) with the 'Maybe from...' as the contact information, rather than my name as is saved on her phone.
Just off the phone from customer services. They are saying they are genuinely clueless as to why this is happening.
They are sending me a new SIM card as they say it can only be a fault with the sim. I’m sceptical however as they only did this to appear to be “doing something” as I told them to cancel my contract if they couldn’t fix it!