Hi Jodi. Thanks for your reply.
The issue is that the total for the latest bill is too high.
We understood that there would be 2 bills, one for Virgin and another for O2 and was told the total price. This was confirmed by Virgin Media while trying to sort out the O2 sim not being sent out - 2 bills with the total of them both being the price quoted and agreed on.
Have just been emailed the latest bill and the Virgin Media price is the whole total which is wrong. It should be the quoted price minus the o2 bill price.