AT&T has the Lumia 925 (RM-893, same one you guys have), uses visual voicemail, and uses the same cell technology as you guys and released the update over a month ago. . Its funny how everyone else hasn't had much trouble getting their apps and phones to work.
So basically the Wi-Fi Calling app is so bad that you guys have to wait forever to fix it? The Band-Aid to the bad coverage is the reason why you guys can't get phone OS update out in a reasonable amount of time. Yep, this is a great way to retain customers.