Your customer number is unlikely to have changed with the move to Virgin Media, although any direct debits will now show up as VM rather than ntl. Have those been collected normally?
For a fault it's not worth trying email, the email will not get a priority look at, especially when things are busy. Phone is the best route. I suspect phone lines are very busy because of the Sky One type mess, but you need to persevere to find out what they actually say.
oh and

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