Wednesday, June 01, 2016

AT&T iPhone Voice over LTE "Call Failed" with iOS 9.3.2

Around the time I upgraded my iphone 6s to iOS 9.3.2, I lost the ability to make and receive calls. Other cellular functions worked fine: data and SMS. But I couldn't make or receive calls. When I tried to make calls, it would report "Call Failed".

AT&T first replaced the SIM card (and, of course, updated the IMEI in their mobile switch provisioning), and that restored service for a few minutes before the problem returned.

I erased all data and setting on the iPhone, set it up as a new iPhone, and still had the problem.

Apple then replaced the entire iPhone, and that restored service for a few minutes.  Again the "Call Failed" problem returned.

When I was unable to make the calls, any calls to my cell phone would go to an AT&T Treatment Recording, but if my phone were completely powered off, those calls would have gone to voicemail.

I found through testing that if I turned off VoLTE calling, switching it to "Data Only," then I could make calls. But with LTE for "Voice and Data" turned on, I could not make calls.

Eventually, a dedicated AT&T store representative worked his way through many call transfers to a technician who removed the "news you can use 911 TTY" SoC Code from my cellular line. When they removed this feature, I was again able to make VoLTE calls.

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