Ruckus Wireless supports RADIUS Accounting with interim updates and CoA-DM Messages. We can send RADIUS accounting data to your RADIUS auth / acct / billing system and will disconnect a user when the RADIUS server tells us to. This method does allow some data leakage though, as interim updates are only sent every few minutes.
If you are looking for true volume based cut-off with no leakage, then you should investigate a Hotspot Gateway solution like Nomadix, Ucopia, Mikrotik, Untangle etc.
Often these gateways will have additional specialized features like property management system integration etc for verticals like hospitality.