Microsoft is investigating data usage by Windows Phone 7 devices after internet forums have been flooded with complaints about unidentified data use charges.
Some Windows Phone 7 (WP7) users have complained of excessive data usage charges of up to 50MB a day for checking email and social networking sites on a 2GB data limit plan, leading to speculation of a bug.
In a statement, Microsoft said, "We are investigating this issue to determine the root cause and will update with information and guidance as it becomes available."
Paul Thurrott, Microsoft commentator and author, said in a blog post, "Basically what's happening is that the phone is utilising the 3G data connection even when Wi-Fi is available. It's not clear what apps or parts of the operating system is causing this, but it's definitely widely-reported."
Thurrott added that, after tracking his own Windows Phone data usage, he suspected it might be tied to Windows Phone 7 Marketplace app store. He also quoted a user who complained their phone sends "between 30 and 50MB of data".
Microsoft launched Windows Phone 7 in October last year for nine different handsets. The company recently admitted it was only "comfortable" with WP7's progress after phone manufacturer sales reached 1.5 million.
The first of several updates to WP7 will be available in the coming weeks.