In March, Microsoft announced its release of the Windows 10 Mobile upgrade for a limited number of devices. Among the list of Windows Phones approved for the upgrade was the Lumia 640 XL, but owners of the device on AT&T have faced a seemingly interminable wait for the update to be made available for them.
While Microsoft is able to deliver most updates to its devices without carrier interference once the new OS has been installed, the upgrade from Windows Phone 8.1 to Windows 10 Mobile does require carrier approval. AT&T approved the rollout of the Windows 10 Mobile upgrade for the Lumia 640 in early June, but it's not clear why it's taken the carrier a further five months to bring the update to the larger Lumia 640 XL.
But now, over seven months after it was originally released, AT&T has finally made Windows 10 Mobile available to the 640 XL. The carrier actually approved the update last week, but due to the 'opt in' requirement of the upgrade, no notifications are being pushed to handsets to inform users that it's available. Only in the last 24 hours have comments appeared on Reddit from users who discovered that they could finally upgrade their Lumia 640 XL handsets.
Microsoft expects users to find out for themselves when the Windows 10 Mobile upgrade can be installed on their devices, and then download an 'Upgrade Advisor' app from the Windows Store. This app performs a simple check on the device to enable the user to download and install the upgrade - but without a notification to inform them of the update's availability, many users remain unaware that they can actually install it.
You can find out more about how to upgrade your handset to Windows 10 Mobile here. Once installed, you should find that your Lumia 640 XL has been upgraded to build 14393.321 of the OS.