AT&T are planning to target a number of their Windows Phone devices with the “Mango” update on September 27, according to reports.

AT&T Windows Phone users should expect to see update notifications from September 27 for the HTC Surround, LG Quantum and Samsung Focus 1.3 devices. WPCentral reports that AT&T will be rolling out Windows Phone 7.5 “Mango” to the HTC HD7S in early to mid-October and the revision 1.4 version of the Samsung Focus should receive the update by the end of October. WPCentral received information straight from an AT&T source and it appears that the Dell Venue Pro may see updates directly from Dell.

Microsoft revealed earlier this week that Windows Phone 7 users should expect to see the Windows Phone 7.5 “Mango” update within the next two weeks. Microsoft warned users not to install leaked copies of Windows Phone 7.5. “Every Windows Phone will also receive software from the handset manufacturer,” explained Microsoft’s Eric Hautala. “Since your phone requires the proper firmware to function as designed, my advice is simple: steer clear of bootleg updates and homebrew tools.” Copies of Windows Phone 7.5 RTM builds have been made available for various devices over the past several weeks.