read what it says on the page. you can only cancel by either calling them or by writing to them at the supplied postal address there is no email option.
All you need to do is call Virgin Media and select the option ‘If you’re thinking of leaving Virgin Media’. Call150from your Virgin Media telephone or call0345 454 1111from any other phone to cancel. For more information, do check out ourVirgin Media customer service numbers page.
Or you can write to:
Virgin Media Sales Operation Support Diamond Plaza, Daleside Road Nottingham Nottinghamshire NG2 3GG