@hTideGnow @Dunkman
I'm not convinced that's always true. Public Mobile (Telus) might not be able to guarantee the data is accounted for (and billed) until midnight ... but they often can update the billing information almost realtime.
I've had my Self-Serve summary open on a desktop while using data on a smartphone. Refreshing the page every few seconds is often enough to get the most recent information. I suppose it depends a lot on where you are, the data capacities of the cell site(s) you're connected to, the sync-with-billing capacities of the cell site(s) you're connected to, etc. The info seems to always be updated fairly quickly when I do my thing in Telus-heavy municipalities around GVRD and FVRD.
@Sharonzxy
Another possibility is that you have an app or service on your phone which sneaks a little data every midnight. Some sort of communication with an internet server, report to the mothership and check the latest gossip. All sorts of background updates, syncs, checks, notifications, and telemetry wares are built into smartphone operating systems these days - iOS and Android, Apple and Samsung and Google and other are all happy to leech or burn your data for their purposes. Your phone probably has built-in data usage/monitoring software somewhere which will let you identify which particular thing is using your data in that time window. (I'm guessing that the sneaky-midnight-data is probably a weather app grabbing information about what to display the next day, every day - but I could be wrong.)
