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iPhone XS Max dual Sim roaming issue

I travelled to Japan last weekend and used a foreign roaming Sim as travel Sim for data usage. On arrival in Japan, I disabled airplane mode, changed mobile data to travel Sim in settings, then activated data roaming.

With mobile data set to the travel Sim, data usage is not supposed to be incurred on the primary Sim. I received messages from the primary Sim carrier that my data roaming package was activated. After arriving home, I switched the mobile data back to the primary Sim, It shows that I've used 165GB of data in Current Period Roaming. It's not even possible for a 2-day trip. I switched mobile data to travel Sim and the figures were the same.

I called the carrier to check the data roaming history, 27KB was used on the day of arrival in Japan. Therefore I have to pay HK$198 flat rate for the data roaming package. I requested the carrier to waive the charges and they did, now they're only charging for the 27KB used at normal rate which is down to around HK$3.

So there are two problems found in this issue:

1. Switching mobile data from A Sim to B Sim does not fully deactivate data usage on A Sim

2. The mobile data usage figures seem to be inaccurate

Any fix for this? I upgraded my phone to iPhone XS Max because I travel a lot and I want to switch Sim seamlessly without physically replacing Sim cards, but it turned out disappointing. The carrier waived my data roaming package charge because I've been using their services for 10+ years without such history regarding data roaming. I don't know if they'd waive the charges the next time. If I need to remove the primary Sim everytime while travelling, what's the point of buying a dual-Sim phone?

iPhone Xs Max, iOS 12

Posted on Sep 25, 2018 5:04 AM

23 replies

Jan 27, 2019 12:15 AM in response to SanjayGoenka

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).

FelipeV

Level 6

10,660 points

Sep 25, 2018 5:10 AM in response to Kartoffelplastik

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.

Oct 4, 2018 7:13 AM in response to Kartoffelplastik

I am hoping someone from apple can shed lights on this. I was asking AirSIM this question and they suggest I remove the hk sim whenever I travel to avoid the phone getting confused!! 😱

Fan1226

Level 1

4 points

Oct 21, 2018 9:53 PM in response to lobsterghost1

I got same issue and just report to Apple. Telecom operations rejected to reduce the roaming charge.

SeanTch

Level 1

4 points

Oct 29, 2018 10:33 PM in response to Kartoffelplastik

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.

Fan1226

Level 1

4 points

Oct 29, 2018 10:36 PM in response to SeanTch

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

Jan 16, 2019 6:17 PM in response to K_Maheshwari

Since found another thread that has a workaround. You have to delete all recent calls. Then all calls will be made on the Default line.

Jan 16, 2019 6:24 PM in response to K_Maheshwari

Agree. But unfortunately until someone at apple develops a fix we are stuck with it.

iPhone XS Max dual Sim roaming issue