hi all!
i am using virgin mobile pay as you go and i wanna know the basics of 1899 and if it possible to use it with my virgin mobile pay-as-you-go?
thanks in advance

Yes you can use 1899 from any mobile via their O2O geographical access number. See their rates etc here :
http://www.call1899.co.uk/mobilerates.phpAs you havent got any inclusive minutes because your on Payg ,your be charged to call the access number at the appropriate payg rates,so you have to add this to what 1899 charge you,plus the 3p connection charge of course.
What destination are you trying to call?, their might be a cheaper way.