Today, Sept. 27, AT&T and Microsoft will officially launch a major update for AT&T customers that own HTC Surround, LG Quantum, and Samsung Focus devices.

Earlier this year in March, an update for Windows Phone called “NoDo” was released. The only problem was that AT&T users had to wait almost a month before they were told anything about the update’s distribution. Some Samsung device users had to wait until May to get the update. NoDo was highly anticipated due to the fact that it would allow mobile phone users to use the copy and paste functionality.

The Mango update will include more than 500 new features, such as third-party multitasking, turn-by-turn navigation, Twitter integration, and group messaging.

According to Boy Genius Report, and internal AT&T memo has surfaced, stating the Mango update will become effective on Tuesday:

“Effective September 27, 2011, customers with AT&T branded HTC Surround, LG Quantum, and Samsung Focus devices are scheduled to receive a notification on their device an update is available. The notice will include instructions to connect the device to their PC in order to receive the update. An update for the HTC HD7S is expected by the end of October.”