After a discussion today with Cisco tech support, I learned that the firmware on phones that are registered with the UC320W cannot be upgraded past version 7.5.2(u3). The current version is 7.5.5 and I was unable to upgrade the firmware on my phones. Before Cisco stops supporting the UC320W, Cisco should at a minimum issue a firmware upgrade or a platform modification file to allow users to keep their phones completely up to date.