ONE UI 6.0 Blocks 5G Signals Abroad

[jupeiyun]

I brought unlocked S23u S918UZKFXAA from Samsung for it's support of network everywhere when traveling. I was on CMCC network with 5G on One UI 5.1 and it worked perfectly. However, when I upgraded to One UI 6, you can still found the 5G auto select settings but the actual 5G support is gone.

The 5G sign will show a few seconds but there's actually no network during it. After a few seconds, LTE appear and the network is set for LTE since then. Since it worked on One UI 5.1, so it's definitely a software issue from Samsung and I really hope you could address this ASAP as the network issue is much more significant to daily use. 

[DanG92263]

Perhaps your issue is related to this: https://us.community.samsung.com/t5/Samsung-Apps-and-Services/Phone-app-Crashing-after-One-UI-6-0-up...

Specifically, see number 3

[jupeiyun]

Thank you for the help mate. Will definitely look into it over weekend. Have a nice day 🙂

[KiwiBird97]

Sorry, unfortunately, many foreign networks (including China and APAC networks) are no longer compatible with One UI 6 and later on Galaxy S23 and newer devices sold in the US and Puerto Rico. Going forward, only carriers from the US, Puerto Rico, and parts of Europe will work on those variants. This is a significant change in Samsung's region locking policy since 2017, you know.
(The "Open" carrier cannot be used to substitute for CMCC here, as CMCC is not a US carrier. Once again, the US variants (both U and U1) will STAY LOCKED to the US, Puerto Rico, and parts of Europe, even after five-minute calls.)

There are two options you can consider:
• Enable roaming on your current US carrier
• Buy an SM-S9180 for CN/HK/TW if you will be staying there for a long time

[jupeiyun]

Thanks for the help but I am wondering if the information is from Samsung? Because a software update to implement a new restriction sounds unreasonable as you brought a product and later lost some functionality without any warning. I also tested that on US sim card with roaming and they completely removed 5G support from roaming as well! That's a bad sign even for US users who travels abroad as they lost bands support which is possible from hardware

[KiwiBird97 · Accepted solution]

There was no official announcement on this, but this was quietly implemented to deter bad actors from circumventing the region locking system. To clarify this, the region locking mechanism only applies to the SIM cards and eSIMs being used, NOT roaming. What do those bad actors do when they import those devices? They use tools like Samkey to remove the region locking. It isn't fair that those people have access to those tools, and most of us do not.
(Those SIM restrictions only apply to US variants. International variants will still be able to use foreign SIM cards as usual, including those from CMCC, except 5G support may be limited in unsupported countries.)

[jupeiyun]

Thank you for the nice explanation and I do understand that people use toolbox to use locked phone irresponsibly and that could lead to issues. Although I do hope if I brought them from Samsung US itself, they keep it like international and only apply those restriction to those who benefitted from additional carrier discount. Again, big thank you for addressing the issue, and I already downgraded to One Ui 5.1 to maintain my carrier network.

[novitaforlife]

The area you're in is bad. Go to somewhere like a famous place on a highway and see if that makes a difference