Thanks for your post and apologies to hear that your bill is never what is expected.
We haven't had any price rises since November so any changes will be down to your package discounts, promotions or usage.
If you've made telephone calls that aren't included in your package you would of been charged for these. The same for Pay Per View content. If neither of these then it's possible a promotional discount has ended pushing your bill up.
Checking your bill within My Virgin Media will show you what the charges are for. If you need further help, speak to the team on 150 / 0345 454 1111 and they will be able to go through your bills with you