iPhone 13 Pro iPhone 13 Pro does not always receive incoming call when two lines are active

[pgoelz]

iPhone 13 Pro on ATT (physical SIM), running ios 15.5

I am on ATT and I am currently running the Tmobile "test drive", which installs a Tmobile eSIM as a second line (complete with new phone number) so you can try out Tmobile free for a month. I have ATT selected as the voice connection and Tmobile selected as the data connection, which I believe is the correct configuration.

Last night I noticed I had a voicemail from a known number but the phone never rang. There was no missed call notificaiton either. When I called my ATT cell number, it went straight to voicemail. The phone did not ring and did not show a missed call. If it matters, there also was no ring tone after I dialed my cell number.... there was a silent pause of several seconds and then my voicemail greeting.

Thinking the problem was the Tmobile line, I turned it off and tried again. This time the phone rang as expected. But the next time I tried it, the phone once again did not indicate an incoming call and the call went straight to voicemail.

Subsequent test calls all went straight to voicemail. Note that when this happens, there is no indication from the phone that it received a call.... the lock screen does not light up and there is no missed call notification.

The only way I could restore normal operation was to leave the Tmobile line OFF (with ATT selected as the voice and data connection) and reboot the phone. Since then, it seems to be receiving incoming ATT calls normally.

Since I never had this issue before installing the Tmobile line, I suspect that is the trigger but I don't know if it is the Tmobile line itself or a bug in the ios multi-line operation.

Note that before, during and after having the Tmobile line active, the ATT line was always set as the primary voice line.

Anyone?

 

[Sheepish-Lord]

Interesting configuration but I’ll throw this out there. Do you have WiFI calling enabled? If so, that uses data so this is maybe why your ATT line isn’t receiving calls when the T-Mobile line is enabled. Obviously it could be other things since it’s still in testing it seems but disabling WiFI calling might shed some light.

 

[pgoelz]

Hmmm.... I just checked and WiFi calling is OFF. Plus, I had WiFi turned off when this happened since I was testing the Tmobile data speeds (which were terrible, BTW).

I generally keep WiFi calling OFF just to simplify things if I leave home while on a call.

If my ATT line is trying to use VOLTE, I wonder if that might confuse things because the LTE connection is Tmobile?

 

[grumpy21]

It's not just T-Mobile. I have two AT&T numbers on my iPhone 13 Pro Max, one personal and the other business. I often experience the same thing with my personal line, no indication of a call until I see the voice mail. In my case, personal is the data line and WiFi calling is enabled on both lines.

After noticing the problem, if I ask a friend test-call the personal line with his iPhone, also on AT&T, it goes directly to voice mail. If I test-call on a land line it will ring through. I can't say that will always be the case though. But if I call business, it always rings through. I've found that the only cure is a hard reboot of the phone and even that is temporary. I now just make it a practice to reboot every morning and now have the problem less frequently.

I've had the iPhone in this configuration since launch and this irritating phenomenon only started appearing in the last couple of months. It's either AT&T or the iPhone.

I think that my next move will be to change the data to business and wait to see what will happen.

 

[grumpy21]

I forgot to add that my default voice line is the Business line.

 

[pgoelz]

It's not just T-Mobile. I have two AT&T numbers on my iPhone 13 Pro Max, one personal and the other business. I often experience the same thing with my personal line, no indication of a call until I see the voice mail. In my case, personal is the data line and WiFi calling is enabled on both lines.

After noticing the problem, if I ask a friend test-call the personal line with his iPhone, also on AT&T, it goes directly to voice mail. If I test-call on a land line it will ring through.

Interesting since that is the opposite of my configuration. In my case, the line that fails to ring is the VOICE line.... the same line that has ALWAYS been my voice (and data) line. Not sure about the Tmobile data line since the number associated with that line is just a temporary number and no one calls it.

Fortunately, this is just a temporary situation for the duration of my 30 day Tmobile test drive. I do not plan on having two lines active after that, so hopefully this aberrant behavior will cease.

 

[grumpy21]

I'm glad that it's not something that I'm doing wrong. In the end, I suspect that AT&T is the problem. They really don't seem to have e-sims worked out entirely.

 

[pgoelz]

Well, to further confuse the issue..... this evening I had an outgoing SMS fail to deliver. When I checked, I found my signal going from no bars / no service to one bar. When I called ATT I found out that the network in my area was showing status RED and two towers near me are under maintenance with severely degraded service. Supposedly has been going on for a couple days on one tower and more than a week on the other. Was this a contributing factor? Very possibly.