Early reports are coming in from select users that the latest Insider build for Windows 10 Mobile – build 10586.63 – may have a bug related to Messaging backup that causes excessive cellular data usage.
Starting a few days ago, users have begun to notice that their cellular data pushing towards 1GB in just a few days.
Over at reddit, a few users pinpointed the data leak to Messaging syncing, and history found in Settings. However, neither have been verified by Microsoft at this time although the company is evidently aware of the issue affecting some users.
As a precaution, users can disable Message History & Sync through the following steps: