iPhone 13 Pro's recurring 'No Service' and 'Cellular Issue Detected' on iOS 18

Device: iPhone 13 Pro

iOS Versions Affected: 18.2, 18.3.2, 18.4, 18.4.1

Symptoms: “No Service”, “Cellular Issue Detected” in Settings, signal sometimes randomly returns, but problem keeps recurring

After updating to iOS 18.2, I started experiencing intermittent loss of all cellular service—the phone displays “No Service” and Settings > Cellular shows a “Cellular Issue Detected” warning, even when the device occasionally works normally. Sometimes the problem resolves itself after a few hours or days, or even weeks (signal comes back for a while, sometimes for weeks), but it always returns eventually.

The SIM card is recognized in Settings (IMEI and carrier info visible), but no signal bars and no option for Wi-Fi Calling (menu doesn’t appear unless service is working).

At times, usually after each update, the phone overheated and had severe battery drain for days/weeks (seemed to be related to the modem/baseband trying to reboot and fix itself). Eventually, the signal would return, and the overheating/battery drain would no longer occur, and work fine e.g. 5G/calling etc all good.

The issue is that I'm now in a “semi-broken” state: no overheating or battery drain, but still no service, it just decided to go away for some reason. Reluctant to update to 18.5 because I feel that will put it back into the overheating broken state.

I have updated iOS multiple times (now on 18.4.1), reset and restored the device, reset network settings, toggled airplane mode, and switched between 4G/5G. Nothing resolves the issue permanently.

It has been extremely annoying to deal with, having missed important calls due to the outage. This issue is unpredictable and unreliable for daily use.

I eventually went to the Genius Bar, who quoted £459 for a full internal replacement (minus the display). This is ridiculously expensive, when everything else with the phone is in perfect condition, 95% battery health etc. I do not need a replacement battery or back, just a logic board/modem change.

They gave 2 options:

Pay for the full replacement fix, but I was warned by them that this issue could happen again, and the phone is not covered by warranty after 90 days, so this does seem quite worrying.

Buy a new phone. How do I know that it won't happen on a new device?This problem is appearing on newer iPhones too (e.g. iPhone 15/16 Pro per forum reports).

TLDR:

This “No Service”/“Cellular Issue Detected” issue is widely reported by other users on iOS 18.x, including on newer models.

In my case, sometimes the signal returns randomly after days or weeks of no service, with no pattern or obvious trigger (no update, no restart, no SIM change).

Questions:

1. Is there a permanent fix or confirmed cause for this issue?
2. Why does the phone sometimes recover on its own, and why does the “Cellular Issue Detected” warning remain even after apparent recovery?
3. Are there any official Apple repair/exchange programs for this bug, or is Apple investigating a software/firmware fix?
4. Is there a way to force the modem/baseband or carrier profile to reset, beyond the normal network reset and SIM re-insertion steps?

Any insight from Apple or the community would be appreciated, especially for users who’ve fixed this long-term.

[Re-Titled by Moderator]