For example, if you started using Virgin Media on the 11th of February and your account has been set to bill on the 21st of February, then your next bill will include a charge from the 11th February to the 20th February (extra 9 days). These extra days charged will be noted on the first page of your bill under “Summary of Charges”, and at the top of your bill and in the service charge section.
The same goes for if you have recently changed your service part of the way through the month.
You could have also purchased On Demand movies. The details of the movies purchased within the billing period will be displayed in the "Your Usage last month" section, including movie title, date and time of purchase.
There’s also the possibility that a promotion/discount came to an end. If this is the case, then the details of the promotion/discount will be listed in the "Savings and Discounts" section on your bill.