Do you know anyone else with a Virgin phone? If so put your SIM card in their phone and see if you can receive a message. If you can then the problem is with your phone. If not then there is something wrong somewhere at Virgin.
You will have to call them, explain what has happened and what the chap at Virgin has already done. Or you could take your phone into a Virgin store and ask them to have a look.
It must be very frustrating for you, i hope it gets sorted soon.