iOS 27 update mobile network issues

iOS 27 Cellular Network Instability – Network Keeps Dropping and Calls Affect Reconnection

Hi everyone,

I’m experiencing a serious cellular network issue on my iPhone 15 after updating to iOS 27.0. Everything was working normally before the update.

The network keeps automatically refreshing/re-registering. For example, the phone may show 5G/True 5G, then suddenly switch to No Service/no signal for 1–2 seconds, then the network comes back again. This keeps happening repeatedly. Sometimes the network may remain available for a short while before dropping again.

There is another unusual problem with calls.

If the network comes back and I immediately make or receive a call, the call connects normally and I can continue talking. Even if the network indicator becomes unstable during the call, the call itself does not immediately disconnect.

However, as soon as the call ends, the cellular network disappears again and the phone returns to No Service. The phone then has to wait until the network automatically comes back before I can make or receive another call.

Because of this, I sometimes have to wait for the network to appear before making a call.

This is not a situation where the phone stays without service for 4–5 minutes. The network can change very quickly — for example:

5G/True 5G → No Service for 1–2 seconds → 5G/True 5G → No Service → network returns again.

I have already tried:

Network Settings Reset

Restarting the iPhone

Completely powering it off

Factory Reset

Testing both 5G and LTE

Testing a Jio SIM

Testing an Airtel SIM

The same issue occurs with both Jio and Airtel, while the Jio SIM works normally in another phone.

I also ran Apple Mobile Diagnostics multiple times. Every time, it reported:

“Diagnostics detected a software issue.”

The diagnostic screen showed iPhone Hardware as passed/green, while Mobile Service was flagged.

I have also noticed unusually high battery drain with very little usage.

Has anyone else experienced this exact behavior after updating to iOS 27.0, especially the part where an ongoing call can remain connected but the cellular network disappears again immediately after the call ends?

Could this be related to the iOS 27 cellular/modem software or network registration process?

Phone 15 Pro Max – SIM/eSIM issue after iOS 27 update

I have an iPhone 15 Pro Max that was working normally before updating to iOS 27. After the update, the SIM/eSIM works fine for around 2–3 days, then suddenly one SIM disappears and the other shows “Invalid SIM.”

I’m using a travel/data eSIM, and the phone is carrier unlocked (“No SIM restrictions”). The EID, IMEI/IMEI2 and modem firmware are all showing normally.

When the issue occurs:

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• One line disappears.
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• The other shows Invalid SIM.
• 
  
• 
  
• Control Center shows Invalid SIM / No SIM.
• 
  
• 
  
• Deleting/reinstalling the eSIM temporarily changes the SIM entries, but the problem returns.
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• I have also Reset Network Settings, but it did not permanently resolve the issue.
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• I eventually deleted all eSIMs, but the phone still showed the same Invalid SIM / No SIM behavior.
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The strange part is that everything works normally for 2–3 days before failing again, and this started only after upgrading to iOS 27.

Has anyone experienced the same intermittent Invalid SIM/No SIM issue after iOS 27 on iPhone 15 Pro Max, and found a permanent fix?

The moment I updated the ios to 27 both my sims stopped working together. If u switch off one of them, the other works fine. I have since been trying everything in my capacity to fix this. I have contacted apple support, did everything they asked me to do.I have even visited service centres, where apple has only trained their engineers one thing. Any problem you are facing, we will update your software. If that resolves your issue, its fine. If not, that’s yours to handle. We do not know beyond this. So now, after trying everything and spending money on something which was not even my fault, m still stuck with the issue with no help at all. I really hope apple comes up with a solution asap!!

Same here, in Madrid, Spain. Since I updated to ios 27 calls get’s finished sudde nly or I can not call. Also data is impacted, really slow speed in carrier data mode, wifi works fine.

Sol Apple Store says is my carrier, but I know lot of people facing same issue since they updated. Shamefull.

Not resolved after complete restore, configs and data. Iphone 17. Apple does not provide any solution. Same SIM card working fine in Redmi Note 14. Shameless. Xiaomi 1 - Apple 0 🙂

edit: I don’t use any VPN

I am having an issue with my iPhone 17 Pro Max in Kosovo after updating to iOS 27.

I am completely unable to make or receive cellular calls, even though my 5G mobile data and SMS text messaging are working perfectly.

My carrier, Vala, confirmed that everything is fine on their end and stated that this is a bug with the iOS 27 update. I have already tried standard troubleshooting steps, but nothing has resolved the issue. The iOS 27.0.1 update did not fix it either.

I have a iPhone 15 pro max. Updated to iOS 27, and since then my WhatsApp calls drop, I keep getting messages saying ‘poor connection’. I tried everything, resetting the network settings, resetting the phone, even having problems with wifi connection, and social media posts are loading slower or buffering. Any advice please??? Thank you

I am also facing same issue. I have tried all the possible ways even though re-installed e-sim but nothing helps after updating to ios 27.

If any help would be valuable.

I am using iphone 14

Thanks in advance

Ios27 update on iPhone se3(2022)

result is Meta application like Facebook Instagram whatsapp tell Connect to internet , in Fact not possible to use it on wifi or 5g it’s the same with Spotify, only duolingo works perfectly is it due to Meta apps or iOS 27?

This update is a nightmare. I usually avoid updates, but I don't know why I opted into these iOS 26.7 and then iOS 27 updates. Now I'm facing the same issue: no network and no calls. I've tried almost every solution I could find online.

I really hope Apple releases a fix for this soon.

After the ios 27 update my cellular network signal problems

from the past 3 days no signal i tried every trick

now i purchase the new android phone and convert the e-sim to a physical sim

waiting……… for new update 😂😂😂🙈

iPhone 15 Pro Max (eSIM-only) – SIM/eSIM issue after iOS 27

My iPhone 15 Pro Max is an eSIM-only model and was working normally before updating to iOS 27. After the update, my eSIM works normally for around 2–3 days, then suddenly one eSIM disappears and the other shows “Invalid SIM.”

The phone is carrier unlocked (“No SIM restrictions”), and EID, IMEI/IMEI2 and modem firmware are all present normally.

When the issue happens, Control Center shows Invalid SIM / No SIM. I have tried restarting, deleting/reinstalling eSIMs, and Reset Network Settings. These actions may temporarily bring the SIM entries back, but the problem returns after a few days.

I have tested with newly issued eSIM profiles as well, so it doesn’t appear to be a single faulty eSIM.

The strange part is that the eSIM works perfectly for 2–3 days and then suddenly stops, and this started after updating to iOS 27.

Has anyone with an eSIM-only iPhone 15 Pro Max experienced this intermittent Invalid SIM / No SIM issue after iOS 27? Looking for a permanent solution or confirmation of whether this is an iOS/modem issue.

Apple very bad this is ridiculous update ios 27 it’s been 1month there is no response from apple after update dual sim problem started Internet doesn’t work when both sim are on and after sec 1sim network goes away When one sim turn off den only the Internet work … very 3rd class update from apple .. I thing 6k android phone work better in dual sim then this …. When apple will response.

I am also facing the same issue. Mobile data doesn’t work with dual sim active. It works only if I disable one the sims. Tried everything including reset all settings and delete the old ones. Nothing worked. Having 14 pro max