Microsoft said it is investigating why some mobile handsets running its Windows Phone 7 software are sending and receiving "phantom data".
The software maker’s spokesman was quoted by BBC News as saying the company will determine the root cause and will update with information and guidance as it becomes available.
The mobile operating system aimed at the consumer market was launched in October 2010.
Many users in the US have posted complaints on several online forums saying that their phones are automatically sending about 30MB to 50MB of data every day.
Other users said data transfer occurred mysteriously in the night when they do not get any e-mails.
BBC quoted people who said the problem may be because of phones sending feedback to Microsoft about the software’s performance or because the phones were using a 3G connection even when wi-fi was available.
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Windows Phone 7 is reportedly Microsoft’s best answer to competing OS from Apple and Google.
