iPhone XS Max dual Sim roaming issue

Had the same issue on a recent business trip to Shanghai where I was using a HK/China SIM in slot B and my normal Hong Kong Smartone SIM in slot A. The card in slot B required data roaming to be enabled as its primary country is HK and not China. Prior to enabling data roaming I made sure to switch data to the HK/China card and make my normal HK card the "voice" line.

To my surprise, I was charged for daily data roaming on the HK card despite routing all data through the other SIM - or so I thought.

Called Smartone today to dispute the charges, explaining the problem to them. They were already aware of such cases and were happy to immediately credit my account for the full roaming plan charges. Further, they advised that Apple had told them that his issue is resolved in iOS 12.1 but recommended to remove the HK SIM card next time if the other SIM requires data roaming to be enabled. Obviously, this is a poor solution and defies the whole point of having dual SIMs in the first place (at least for my travel use case).

So I recommend you get in touch with your mobile phone carrier to contest the charges and upgrade to 12.1 if you haven't done so already!

The small roaming data issue (0.1-3K) is due to the roaming authentication mechanism. When a sim with data roaming capability reach another country, it will automatically make use of the foreign local cellular network to send a request checking whether the sim is authorized to use data in that country, despite what you've set in your whatever phone. That request consumes the small roaming data, and is invisible to user. That's why users are advised to remove the sim.

I just told my carrier to disable data roaming and only enable voice roaming to avoid dispute.

Did you turn off the "Cellular Data Switching"? If this was on and you got a call, your data would jump to the other line and that might explain the 27kb usage.

This is soo simplee and sweet ..

under yr mobile data option on yr phone . Thr is a switch of Mobile data switching .. this switches yr mobile data to anthr simcard when the other sim is on a call ... i hope u got this easy xplantion ..

jz switch that off .. and never have the issue !!!!

Solution was to re-insert original SIM (from Ooredoo) which created another plan, then remove the SIM. Or according the technical support, you have to delete the eSIM plan, and recreate eSIM plan again. I guess this going to be a challenge whenever you roam another country.

Incurring costs all the time while I travel. Even after clearing recent callls, my phone still reverted to UK sim even though default is set to US sim.

My UK account shows data used as well even though roaming switched off and so is data switching.

Back in UK soon so will be calling Apple. Someone has to fix this issue.

To me, they have designed the dual sim functionality purely for the people that have business and personal mobile numbers in their home country. This functionality is not working for international travellers.

Looks like i me I am going back to changing physical sims - so AT&T likely going to charge me again to switch back to a physical sim.

No one from Apple is here. We are all users like you. If you want to speak or chat with Apple use the Contact Support button at the top of this page. Or call Apple Support (in the US) at: 1-800-MY-APPLE

I have exactly the same problem. IOS 12.1.2 on an iPhone XS. I have data only active on the eSIM, but daily, a few Kilobytes, pass over the physical SIM. I have Roaming deactivated, and also "Cellular Data Switching" is off!

To avoid the roaming costs, my only option is now to switch off the physical SIM completely.

But what's the point in having a Dual SIM phone then?! Did anyone got some news on this issue?

My US iPhone XS has a AT&T SIM card and a German T-Mobile eSIM. I'm traveling in Europe quite often.

I have the same two problematic issues described here:

1) When traveling abroad, time I turn on the phone or enter another country, AT&T charges me the $10 intl. data day rate even tough data is turned off for AT&T. This month I have accumulated $60 already.

2) I'd like the use the local SIM for outgoing calls and data while the other number stays active for incoming voice calls only. It seems to be impossible to do this. I always have to manually select the outgoing phone number.

1) Is a bug and 2) is a UX problem; whoever designed it never thought of people who are traveling. The right way to fix 2) would be to select the default data and voice line manually (or automatically based on location).

Assuming you have the Chinese dual SIM phone as eSIM mode is not yet "live", read this to see if it helps:

Using Dual SIM with two nano-SIM cards - Apple Support

Hope this helps.

Yes, off. Number of users have this problem and confirm it is the bug of the iphone as this happen on different telecom operators.

My problem is with eSIM. I purchased my Xs Max from Ooredoo Qatar, and I enabled eSIM and traveled to Tanzania. Phone worked fine in roaming mode in local carrier (Airtel). But since I am back in Qatar, all my local call shows as coming from Tanzania. It just shows local number (which normally shows the names from Contact), and Tanzania written underneath it. Carrier selection and all setting show as connected to Ooredoo - local provider. I have a case opened with Ooredoo.

Sharing as FYI.

I have similar problem. When I select 'Default Voice Line' in Cellular setting, I found that all of my contacts do not switch to Default line which I have selected but few still dial from the sim which is not default sim. This has costed me heavily on roaming charges.

I found that when I was in earlier country which ever calls I made from my that country sim and the call are in Recent call list, still remain on that country sim and do not follow my selection of 'Default Voice Line'.

This is a big defect in UI of iPhone and need urgent correction.

I have the same experience. The auto Last Number used picks up my home number but I would expect when default line is set this should switch all numbers to the travel sim. Yes you can number by number go through your contacts and set to “Always Us” but this is just non-value added.

Default should mean Default.