A Newbies Question About Cost and Download Alowance

New to VT in general, but have been attracted to Roll20 for 2 main reasons. 1) Free to players. 2) non system specific, as we are playing 1e D&D. But more than one of my player are on limited download internet contracts. So my question is will playing on line impact there down load allowance or is it just like surfing facebook ect.  Many thanks,in advance, to those who reply. 

Just off the top of my head at this but as long as you don't use a lot of graphics it should be similar to facebook in terms of bandwidth data allowance. I'm guessing that they are allowed so many gigs per month of use.

Then again, That will be a problem with any videobased communication. But if they usually have at least 300 MB left end of month, I wouldn't worry about using audio, which is the same, it would be equally heavy on the usage as any audio-usage.  Riley can of course correct me if I'm wrong, but I don't see any reason why Roll20 should be heavier on the line with audio/video than other.  When I stream podcasts, I get around 25 MB an hour, which should be a good estimate :-) so with 300 MB you can play roughly two sessions at 6 hours with voice only :-) 

Thanks one and all for your quick answer.