iPhone 15 Cellular Data Instability with Dual SIM/eSIM After iOS 27 — Airtel India

To check the issue you described, I performed a similar test on my iPhone 13 running iOS 27. I already had one eSIM installed, and I have now added another physical SIM alongside it to test the Dual-SIM configuration.

I tested Mobile Data on both SIMs individually, and I am not experiencing any difficulty accessing cellular data on either line. Both SIMs are working normally.

Although I have labelled one of the SIMs as “Travel,” this does not mean that the SIM is currently roaming. The label is simply the name assigned to the cellular plan. Both lines are operating normally under the current configuration.

Images 13 and 14 also clearly show that both SIMs are Airtel SIMs. Therefore, this is not a test involving two different operators such as Airtel and Jio. I am using two Airtel lines simultaneously—one physical SIM and one eSIM—and Mobile Data is working normally.

Also, as you can see from the screenshots, my iPhone 13 with Dual-SIM (1 physical SIM + 1 eSIM) shows the same signal strength on the signal bars for the active cellular lines. The same type of cellular signal indication should be visible on your iPhone as well. The signal bars indicate that the respective SIM is registered on the cellular network and the approximate signal strength being received.

However, it is important to distinguish this from actual Mobile Data performance. A good signal-bar indication does not by itself guarantee that cellular data is functioning correctly. A phone can have a strong cellular signal while still experiencing a problem with data services, carrier authentication, routing, or the carrier configuration. Therefore, the signal bars are useful evidence of cellular connectivity and signal strength, but they do not alone prove that the data connection is healthy.

Based on my test, it is therefore possible that the problem you are experiencing may be specific to your particular iPhone 15, its modem/carrier configuration, or the interaction between that device and the Airtel/Jio eSIM configuration, rather than being a general iOS 27 Dual-SIM/eSIM problem.

There are also two important settings that you have not mentioned in your post, and these can potentially affect how Mobile Data behaves when two SIMs are active:

1. Allow Mobile Data Switching — May be OFF

Please check the setting shown in Images 5 and 12. If Allow Mobile Data Switching is enabled, the iPhone can dynamically use the other line for cellular data under certain circumstances. For a controlled test, I would recommend keeping this OFF, so that the iPhone remains strictly on the SIM you have selected for Mobile Data.

2. Data Roaming — May be Disabled on one SIM

Please also check the Data Roaming setting shown in Image 13. The roaming status of each cellular plan can affect how that particular line handles cellular connectivity. For comparison, it would be useful to document whether Data Roaming is enabled or disabled on each individual SIM/eSIM, rather than simply stating that the phone itself is not roaming.

For a meaningful comparison, I would suggest testing with the following information recorded:

Please check the bandwidth that you are getting. Disable WiFi before running this Field Test.

You may check the current LTE band/5G/4G/3G by dialing *3001#12345#* pressing the call button. See the pic below

Since my iPhone 13 on iOS 27 is functioning normally with two active Airtel lines, this test does not reproduce the problem described in your post. It therefore raises the possibility that the issue may be device-specific, carrier-profile-specific, or related to the particular Airtel/Jio combination and configuration on the affected iPhone 15.

A controlled comparison of these settings would help determine whether the problem is actually related to iOS 27/Dual-SIM generally, or to a more specific combination of iPhone model + modem firmware + carrier/eSIM configuration + cellular settings.

Take your device to an Apple Retail Store or Apple Authorized Service Provider, or contact Apple Support:

Find Locations - Location Selector - Apple

Contact Apple for support and service - Apple Support 

Hi Amogh,

I also had exactly same issue so I can understand how frustrating this is, I have 14+

I came across one possible reason that was, after update system is facing dual sim network conflict issue so as suggested I removed one physical JIO sim and tried again

It worked, my primary sim AIRTEL worked properly.

I will try reinserting 2nd jio sim tomorrow again to check if it works or not.

but at least for now i can use my primary sim for call and internet.

sms will be activated after 24 hrs as per airtel process after esim profile installation

fingers crossed.

all the best

NB: I installed my esim profile twice on same day by visiting airtel office, so you can try the same.

Been experiencing the same issue on my 16 Pro, although the status bar shows 5G, however running the network tests including dialling *3001#12345#* shows that I’m on LTE network. Visited Airtel store for this, they tried to send fresh backend network configuration- but nothing seems to work. Facing this issue after iOS 27 update.

I am currently facing the same issue with my iPhone 16, while I use Dual sim, my physical sim is sometimes not reachable.

I experienced this after upgrading to ios 27.