Microsoft has said that the phantom data transfers experienced by some Windows Phone 7 customers is the fault of a third-party application.
Reports earlier this month suggested that data was being requested by the handsets without user interaction, accounting for up to 1.5GB per month.
"We have determined that a third-party solution commonly accessed from Windows Phones is configured in a manner that may cause larger than expected data downloads," a Microsoft spokeswoman told V3.co.uk.
"We are in contact with the third party to assist them in making the necessary fixes, and are pursuing potential workarounds to address the configuration issue in case those are needed.
"At this point in our investigation, we believe this is responsible for most of the reported incidents."
The company declined to name the third-party application, but did say that the percentage of Windows Phone 7 users affected was in the low single figures.
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