Hi,
A quick read of the posts suggests Virgin Mobile are having technical difficulties, though I can't confirm this. Hopefully one of the forum team members will be able to assist you shortly.
I've just recently joined myself, and can't receive any calls or texts after porting my number from BT.
The only thing I can suggest in the meantime is to follow the troubleshooter for your device and see if that helps.
https://devicesupport.virginmedia.com
All the best.