My wife and I each have an iPhone, and hardly ever use 3G. Occasionally, however, we end up going way over out 200MB per month quota. When it happens, the big data usage is always on the 26th or 27th of the month, between 5:30m and 6:30pm, when we're not at home!
It's very odd. We don't watch video or do big downloads when we're not on wifi.
What could we be doing (or neglecting to do) to use 167MB in 25 minutes without even realising?!
I presume the date and time thing is coincidence. But maybe not?
Peter