iPhone XS Max Cellular connectivity goes stale while using dual sim - China/HK Model

itsamacthing

macrumors 6502a
Original poster
Sep 26, 2011
829
456
Bangkok
Recently traveled to Hong Kong, picked up the dual physical SIM XS Max.

Have both my Asia SIM and US SIM installed. The Asia SIM works regionally in Asia, the US SIM only in the USA.

I have both SIMs installed and I am in Asia (Asia SIM connected, US SIM not able to register on the roaming carrier), the iPhone looses its connection while still showing up as connected to the carrier. I have to restart the phone to regain cellular action (voice and data)

I have the Asia SIM setup of primary, the US SIM as secondary.

When I remove the US SIM, this issue does not seem to happen.

New feature in the latest iOS (which I asked Apple why it wasn't there) is the ability to turn each SIM off or on. Seem when I turn the US SIM off, issue is also gone.

What happens to the traveler going in and out of coverage, does the iPhone stop working each time a SIM is unable to connect?

I have many dual SIM phones for the same reason I got this one, have never seen this kind of behavior. The iPhone should be able to manage one SIM not being able to register as that is why many people have dual SIM phones.
 

kgenova

macrumors 6502a
Sep 19, 2013
892
351
Recently traveled to Hong Kong, picked up the dual physical SIM XS Max.

Have both my Asia SIM and US SIM installed. The Asia SIM works regionally in Asia, the US SIM only in the USA.

I have both SIMs installed and I am in Asia (Asia SIM connected, US SIM not able to register on the roaming carrier), the iPhone looses its connection while still showing up as connected to the carrier. I have to restart the phone to regain cellular action (voice and data)

I have the Asia SIM setup of primary, the US SIM as secondary.

When I remove the US SIM, this issue does not seem to happen.

New feature in the latest iOS (which I asked Apple why it wasn't there) is the ability to turn each SIM off or on. Seem when I turn the US SIM off, issue is also gone.

What happens to the traveler going in and out of coverage, does the iPhone stop working each time a SIM is unable to connect?

I have many dual SIM phones for the same reason I got this one, have never seen this kind of behavior. The iPhone should be able to manage one SIM not being able to register as that is why many people have dual SIM phones.
Hi! I have an XR, purchased in China, and used in China, and I'm having exactly the same issue. The phone silently loses its cellular connectivity with no notification to you that this has happened, and the only way to fix it has been to restart the iPhone. I am using a China Mobile as my primary SIM and a US TMobile SIM as my secondary one. I haven't tried removing the US SIM or turning it off--I'll have to give that a try. I've been meaning to bring the phone into the Apple Store about this issue, but haven't gotten around to it. Really irritating, though. So nice to hear that someone else has the same issue!
 

popcorn-in-sac

macrumors regular
Jan 30, 2008
103
23
Seattle, WA area
I think I'm seeing something similar with my non-HK Xs. Using eSIM with Verizon and physical SIM with AT&T in the US.

Coverage for both in my area is not great, and at times have "No Service" for AT&T. I'm finding Verizon (my primary line, and cellular data) often seems to "go away", where it still shows Verizon, still shows signal bars, greyed-out, but still present. No data works at all, typically requiring a reboot to cure, other times the modem seems to reset itself. This is with 12.1.1.

Does this sound like what you are experiencing? Just curious if it's the same basic problem for both models -- the modem is struggling to keep the primary line active while the secondary line is offline/low signal/whatever.

I left feedback for Apple on this issue.
 

kgenova

macrumors 6502a
Sep 19, 2013
892
351
I think I'm seeing something similar with my non-HK Xs. Using eSIM with Verizon and physical SIM with AT&T in the US.

Coverage for both in my area is not great, and at times have "No Service" for AT&T. I'm finding Verizon (my primary line, and cellular data) often seems to "go away", where it still shows Verizon, still shows signal bars, greyed-out, but still present. No data works at all, typically requiring a reboot to cure, other times the modem seems to reset itself. This is with 12.1.1.

Does this sound like what you are experiencing? Just curious if it's the same basic problem for both models -- the modem is struggling to keep the primary line active while the secondary line is offline/low signal/whatever.

I left feedback for Apple on this issue.
I'm not sure if it is the same or not. I'm actually effectively using China Mobile for both lines, because TMobile is roaming on China Mobile. But having the phone show that there is connectivity while actually having none and needing a reboot to fix...yes, that is very unfortunately familiar!!
 

itsamacthing

macrumors 6502a
Original poster
Sep 26, 2011
829
456
Bangkok
Great to see some posts...

I do have a case open with Apple, the senior support is taking this to engineers.

So with 2 Thai SIM cards that can connect to the carrier, phone works fine all day. Gonna test it again today.

With 1 Thai SIM and 1 ATT SIM (the ATT SIM cannot register on the local roaming international network, it only works in the USA with no international roaming) the cellular service on the phone stops working very quickly after reboot. Reboot and repeat, very reproducible.

Before the update to 12.1.1, there was no feature to turn off one sim or another. Now in 12.1.1 there is that very basic feature and that is the quick fix for me, turn off the SIM that cannot register.

Apple says that this is not okay and they are looking into it. Imagine the user with 2 SIM's who has them to gain coverage in various areas that do not have ubiquitous coverage. So lets keep this thread alive, there are potentially a lot of people with the same issue.
 

kgenova

macrumors 6502a
Sep 19, 2013
892
351
Great to see some posts...

I do have a case open with Apple, the senior support is taking this to engineers.

So with 2 Thai SIM cards that can connect to the carrier, phone works fine all day. Gonna test it again today.

With 1 Thai SIM and 1 ATT SIM (the ATT SIM cannot register on the local roaming international network, it only works in the USA with no international roaming) the cellular service on the phone stops working very quickly after reboot. Reboot and repeat, very reproducible.

Before the update to 12.1.1, there was no feature to turn off one sim or another. Now in 12.1.1 there is that very basic feature and that is the quick fix for me, turn off the SIM that cannot register.

Apple says that this is not okay and they are looking into it. Imagine the user with 2 SIM's who has them to gain coverage in various areas that do not have ubiquitous coverage. So lets keep this thread alive, there are potentially a lot of people with the same issue.
So, I got the Shanghai Apple Store to switch out my iPhone XR for a new one, and for a while, things were much improved, and now it is back to silently going dark on me again. So frustrating!!
 
  • Like
Reactions: itsamacthing