Bandwith control

Hello everyone, I'd like to ask for any advice regarding actions to ensuring that a satellite user won't exceed his monthly limit.

This concerns satellite installations in hotels with users that have iphones and galaxy models which will constantly sync with  dropbox and other cloud services, thus consuming the available data per month.

We've come up with a few solutions so far, via a linksys router:
- Blocking known ports for youtube, streams, torrents etc.
- Blocking certain ports apple devices use for syncing
- Blocking certain ports for android devices, google play etc.
- Blocking browser use of dropbox
- Blocking multiple services dropbox uses for syncing files via apps (for example: *.dropbox.com *.getdropbox.com *. amazonws.com and *.softlayer.com)

Still though we are not certain we got everything, as there are mulitple things we are afraid we're missing.

Any advice would be helpful, thanks.