topic Re: Device: Samsung Galaxy S21 FE Issue Duration: 5-6 months (worsening), cal.. in Galaxy S21

Device: Samsung Galaxy S21 FE Issue Duration: 5-6 months (worsening), call completely broken for last 15 days Setup: Dual SIM — Airtel (SIM 1) + Jio (SIM 2

sauravpattnaik674 — Mon, 27 Apr 2026 17:20:50 GMT

Device: Samsung Galaxy S21 FE
Issue Duration: 5-6 months (worsening), call completely broken for last 15 days
Setup: Dual SIM — Airtel (SIM 1) + Jio (SIM 2)

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THE PROBLEM
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Stage 1 (5-6 months ago):
Airtel SIM stopped holding 5G — 70% of the time on 4G despite full coverage. Same SIM works perfectly on 5G in other phones. Jio SIM has zero issues on the same device. This clearly points to a modem/carrier config issue on Samsung's end, not Airtel's network.

Stage 2 (last 15 days — complete call breakdown):
— Outgoing calls not connecting
— Incoming calls ring but cannot be answered
— Even when connected, no audio on either side
— WhatsApp calls work perfectly fine — mic and speaker are NOT the issue
— Restarting phone gives temporary relief for a few hours, then same problem returns
— Occasionally even Jio calls fail

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WHAT I HAVE TRIED
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✅ Restarted phone multiple times
✅ Re-inserted both SIM cards
✅ Reset network settings
✅ Toggled flight mode
✅ Switched SIM slots
✅ Factory Reset — YES, FULL FACTORY RESET — problem returned within hours
✅ Visited Samsung Service Centre

Service centre verdict? "Leave the phone for 24 hours." No explanation of what they will actually fix. No acknowledgment of a known software issue. Just — leave it and come back.

I cannot leave my only phone for 24 hours. And more importantly — what exactly will they fix that a factory reset couldn't?

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WHAT SAMSUNG IS NOT SAYING
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This is NOT an isolated case. A simple search on this very community forum shows:

— S21, S21+, S21 Ultra users all reporting identical Airtel call issues
— Problem clearly started or worsened after security patch updates
— Multiple posts from 2021 to 2025 — FOUR YEARS — with no official acknowledgment from Samsung
— Samsung's only response every single time: restart, reset network, factory reset, visit service centre

Meanwhile the same Airtel SIM works flawlessly in a basic ₹5,000 phone.

I also previously used a Samsung Galaxy A50 — faced the exact same Airtel network degradation after 3 years, which forced me to buy the S21 FE. Now the S21FE has the same issue. This is a pattern, not a coincidence.

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DIRECT QUESTIONS TO SAMSUNG
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1. Has Samsung officially identified and acknowledged the Airtel carrier compatibility issue on the S21 FE series?

2. Is there a specific security patch that broke Airtel's modem/carrier configuration on Indian S21 FE variants?

3. What exactly will a service centre do that a factory reset cannot — will they flash a different firmware version?

4. Since S21 FE is now approaching end of software support, are Airtel-affected users simply expected to buy a new phone?

I am not here for basic troubleshooting steps that have already failed. I want a real answer.

Tagging this as a known issue. If other S21 FE users are facing the same Airtel call problem, please reply and share your experience — the more voices, the harder it is for Samsung to ignore.

Re: Device: Samsung Galaxy S21 FE Issue Duration: 5-6 months (worsening), cal..

liondestroyer22 — Tue, 28 Apr 2026 21:48:32 GMT

Did u try a new Sim card if that doesn't work then upgraded

Re: Device: Samsung Galaxy S21 FE Issue Duration: 5-6 months (worsening), call completely broken for last 15 days Setup: Dual SIM — Airtel (SIM 1) + Jio (SIM 2

sauravpattnaik674 — Wed, 29 Apr 2026 17:53:09 GMT

How it solved ?
along with the 5g issue I am facing below, its really frustrating, same sim works in other phones
— Outgoing calls not connecting
— Incoming calls ring but cannot be answered
— Even when connected, no audio on either side
— WhatsApp calls work perfectly fine — mic and speaker are NOT the issue
— Restarting phone gives temporary relief for a few hours, then same problem returns
— Occasionally even Jio calls fail

Its really frustrating, why its happening for airtel sim only, same airtel sims working in other phone like motoroal, readme phone, I already checked

Re: Device: Samsung Galaxy S21 FE Issue Duration: 5-6 months (worsening), call completely broken for last 15 days Setup: Dual SIM — Airtel (SIM 1) + Jio (SIM 2

Samsung_Moderator — Fri, 01 May 2026 15:39:07 GMT

Hello sauravpattnaik674,
Welcome to Samsung community. I am so sorry to read that you are having tis issue with your Galaxy S21 FE and your Airtel ) Sim card. It can be overwhelming when your Sim stops working and you are unable to use your phone. It appears you have performed the troubleshooting that we would have recommended (http://www.samsung.com/us/support/troubleshoot/TSG10001620). If you have verified that your SIM is working and active, your device requires service. Please visit a Samsung walk-in service center or you can schedule a repair service online

Re: Device: Samsung Galaxy S21 FE Issue Duration: 5-6 months (worsening), call completely broken for last 15 days Setup: Dual SIM — Airtel (SIM 1) + Jio (SIM 2

sauravpattnaik674 — Fri, 01 May 2026 18:33:23 GMT

I am posting this with full diagnostic evidence after exhausting every possible fix

Captured sysdump logs immediately after reproducing the call failure

LOG EVIDENCE — THIS IS NOT SPECULATION

I captured two independent log dumps. Both tell the same story:

From CP_MEMBERS.txt (my sysdump):

IMS deregisters mid call-flow — IMS_NOT_REGISTERED
SIP protocol failure — "SIP SDP Protocol Error" causing call termination with 487 Request Terminated
IMS registration drops and retries in a loop
PDP context for IMS gets deactivated during active calls
TimerF timeout confirming network/IMS signaling failure

From radio_202604272258.log (Samsung Members diagnostic dump):

When connected to Airtel 5G NR SA — mVoiceRegState=OUT_OF_SERVICE, CS domain shows NOT_REG_OR_SEARCHING, IsVoiceCallAvailable=false
IMS bearer repeatedly crashes — fail cause: LOST_CONNECTION(0x10004), tearDownReason=CONNECTIVITY_SERVICE_UNWANTED
Modem firmware version G990EXXSMHZB1 running under OS G990EXXSMHZB5 — 4 version mismatch between modem firmware and OS
Continuous 5G NR SA ↔ LTE oscillation loop breaking voice registration
System crash logged as REASON: debug0x4948 — not a user-initiated reboot, an actual kernel panic Samsung disguises in the log

The pattern is crystal clear:

Airtel connects to 5G NR SA→ Voice registration fails completely→ IMS bearer drops→ Falls back to LTE temporarily→ Calls work briefly→ 5G NR SA reconnects→ Entire failure cycle repeats

Jio SIM on the same device works fine. Same Airtel SIM works perfectly on other phones. This is 100% a Samsung modem/firmware issue.

WHY FACTORY RESET PROVES THIS IS SAMSUNG'S BUG

Factory reset wipes all user data and settings. It does NOT change modem firmware. The problem returned because the bug lives in the baseband/modem layer — not in user configuration. A factory reset was never going to fix this, and Samsung's service centre recommending it as a solution shows they have no actual fix.

DIRECT QUESTIONS FOR SAMSUNG

Is there a known Airtel IMS/VoLTE compatibility issue on S21 FE Indian variants?
Why is modem firmware G990EXXSMHZB1 not in sync with OS G990EXXSMHZB5?
Will a baseband/modem patch be released to fix Airtel VoLTE on NR SA?
What exactly does a service centre do in 24 hours that a factory reset cannot — and do they have a specific modem reflash tool for this known issue?

TO OTHER S21 USERS

If you are facing Airtel call failure, no audio on calls, or calls not connecting — please reply with your firmware version. The more documented cases here, the harder it is for Samsung to stay silent.

This is a modem firmware bug. Not hardware. Not SIM. Not user error. Samsung needs to own this.