@dandecay
To follow up on my earlier reply, I have just spent a long (!!) time on Virgin Media webchat to try to get a definitive answer to this issue.
They have confirmed that the (free) 789 service no longer works outside of the UK and EU Europe.
The alternative they suggest is to use +44 7458 333 789 (at £1.20 per minute!!) or go onto the webchat and they will try to answer any query that you have (my advice: only go on the webchat when you have a lot of time to spare and bundles of patience!).
Hope this helps.