If you want a Virgin phone line, and do everything on line, you can only get the phone line as part of a bundle with something else - broadband or TV.
If you just want the phone line you have to call 0845 840 7777 and looking at the Virgin web page, it works out at £13.90 per month with a connection charge of at least £49.95.
Whatever package you go for, paying by anything other than DD will cost you £5.00 per month, and paper billing will cost £1.50 per month on top of your other charges.
It sounds to me as if he has got a reasonable deal for the phone by taking the broadband, even if he doesn't use it, as long as he is not facing a monthly charge for the broadband as well.