Reports across the Web are surfacing that Microsoft has a serious problem with Windows Phone 7 that may become very expensive for some: the OS seems to use an awful lot of cellular bandwidth, even when idle. This means those with smaller data plans may find themselves in for a shock when their bill arrives.
One user wrote into Paul Thurrott’s WinSuperSite telling he had to put the phone into airplane mode because he was near his 2GB data limit, and copious amounts of data were being used even when idle. Thurrott himself replied that he had noticed increases of data usage.
What’s happening here is that even when on a Wi-Fi network — for whatever reason — the phone is still using 3G for data. Its unclear what applications (if not the entire phone) is doing this, but its a serious and common problem apparently that Microsoft has yet to confirm.