Same problem here - no tickbox for ebilling.
Slightly odd story behind my account. When I signed up for VM, for reasons only known to themselves, they used an old address for the house from their archives, including a house name that hasn't been used for 10 years. O2 on the other hand (it's a Volt package) used the right address. Between them they were unable to match the addresses to allow the Volt benefits to activate. Remarkably, the only way round it seemed to be for Virgin to scrap my old account and start again with the address I'd given them originally when I first signed up. Who'd have thought that both companies are supposed to be in the communications business and indeed be under the same ownership?
Anyway, I've had lots of teary "sorry you're leaving us" messages, a few "welcome to Virgin" ones and everything now seems to be working. I'm just left with billing by post switched on (which I didn't have with my old account), a bill for £1.75 (refunds welcome) and a letter I didn't want. Oh, and no tickbox anywhere to switch to paperless. If there's anything that can be done I'd be very grateful