If you posted from a non VM IP then obviously they wouldn't be able to do anything and would require further information from you, or if you was posting from someone elses connection who is a VM customer, well they would have needed a new modem in your situation anyway![]()
If you post on their forum from a virgin IP then they know you address and have been known to sort out engineers to attend (they did for me). If you post from a none virgin IP then they normally PM you to sort things out.
I guess if your registration details tie up with the IP that your making the forum post from then they know enough to send something with confidence.