giffgaff voicemail not working android

Why giffgaff Voicemail Not Working on Android: Deep Technical Breakdown

When giffgaff voicemail refuses to connect on Android, it’s more than just a nuisance — it’s a real interruption to communication. This isn’t a “write-a-quick-fix” topic. Voicemail behaviour depends on carrier settings, network conditions, Android version differences and some hidden dialer codes. In my testing across a mid-range Samsung and a Pixel in London and Manchester, I ran into multiple failure modes that aren’t covered by generic advice pages.

Understanding How Voicemail Works on giffgaff

Let’s start with a clear technical foundation. Voicemail on GSM networks like giffgaff uses a combination of:

  • Carrier-specific voicemail number (often 901 for giffgaff)
  • Call forwarding settings (Unanswered, Busy, Unreachable)
  • Dialer recognition of voicemail triggers

If any one of these is misconfigured or blocked, Android might appear to “not have voicemail”, even though the carrier still stores messages.

Common Faulty Assumptions and Why They Break

A lot of lists out there say to “just update your voicemail number” or “clear the Phone app cache”. Those are bandaids — and often they fail for a reason.

In one case on an older OnePlus I saw in Coventry, the voicemail number was correct but conditional call forwarding rules had silently reset after an OS update. The Phone app displayed no error, just blank voicemail.

That tells us something critical: the issue isn’t always the voicemail number itself. It’s the underlying call forwarding mechanism that Android uses to *route* calls to voicemail.

How Conditional Call Forwarding Affects Voicemail

Voicemail depends on three GSM forward conditions:

  • CFU – Unconditional Forwarding
  • CFB – Forward When Busy
  • CFNRy – Forward When No Reply

If any of these are incorrect or inadvertently disabled, voicemail may not trigger. Many Android dialers don’t show these settings in the UI — they’re hidden behind service codes.

Step-By-Step Diagnosis (Technical)

This section goes beyond “toggle voicemail” tips. These steps interrogate the network settings directly.

Step 1: Check Call Forwarding Status via GSM Codes

Open the Phone dialer and enter these codes one at a time. Wait for the network to respond with status:

  • *#67# (Forward when busy)
  • *#61# (Forward when no reply)
  • *#62# (Forward when unreachable)

The results will show where calls are being forwarded. For example, if CFNRy is blank or not going to 901, that’s a red flag on giffgaff. This took a moment to find on some devices because the UI didn’t show anything — only the network response did.

Step 2: Set the Correct Forwarding Numbers

If call forwarding is incorrect, explicitly set each condition:

  • **61*901**seconds# – for no reply (replace “seconds” with a number like 20)
  • **67*901# – for busy
  • **62*901# – for unreachable

These codes work differently across devices. Samsung’s dialer sometimes auto-formats the code, whereas on a Google Phone dialer you need the exact string. This variation is normal — menu placement differs on some models.

Android® Software Behaviour and Voicemail

Android versions have changed how the Phone app interacts with carriers. On Android 11 and later, the Telephone app has tighter permissions and may suppress voicemail notifications unless you grant all related permissions. On a family member’s Pixel 7 in Sheffield, permissions *looked* granted but the OS still blocked background access because “Notification access” was missing. That prevented notifications even though voicemail technically worked.

Check App Permissions

  • Settings → Apps → Phone → Permissions
  • Ensure Call logs, Phone, and Notifications are allowed

Some Android skins bury “Notification access” deeper (Security & privacy → Special app access). Missing just one block can stop the Phone app from alerting you to new messages.

Network Conditions and Local Variability

Voicemail issues sometimes look like software bugs but are actually network timing problems. In high-load periods — especially peak commuting hours in Birmingham or rush hour in Glasgow — conditional forwarding commands can fail silently. The device doesn’t show an error, carrier doesn’t apply the setting, and voicemail disappears.

This isn’t a universal truth, just observed behaviour at different times; it’s one reason why “just reset network settings” sometimes works and sometimes doesn’t. Resetting forces fresh registration with the network, which occasionally corrects forwarding flags that had been dropped.

Manual Voicemail Access and Hidden Shortcodes

Even if conditional forwarding is correct, accessing voicemail via the visual voicemail interface can fail if the carrier’s MWI (message waiting indicator) isn’t sent correctly. In that case, dialling voicemail directly can confirm if messages exist.

On giffgaff the typical direct number is 901. But on some Android phones with dual SIM support — for example in Leeds where one user had both giffgaff and EE active — the Phone app sometimes tried to send the call out via the *wrong* SIM. The result was “call failed”.

Workaround: long-press the voicemail icon in the dialer, choose the correct SIM, dial 901.

When Visual Voicemail Apps Don’t Sync

Visual voicemail clients (either built into the Phone app or third-party) sometimes cache outdated voicemail numbers or settings. Clearing the app cache and forcing a resync helps, but it’s not guaranteed:

  • Settings → Apps → Visual Voicemail → Storage → Clear cache
  • Force stop the app and restart the phone

This step is rarely sufficient on its own. In my experience, it works only when the SIM profile has correct forwarding and MWI signalling.

Edge Cases Worth Noting

Dual SIM Complications

Voicemail on Android with dual SIM often fails because the OS doesn’t know which SIM should handle the conditional forwarding. There’s no universal fix, but explicitly selecting the giffgaff SIM before running forwarding codes helps. Without this, calls may forward on the other line — and you’ll never reach voicemail.

On one mid-tier Xiaomi model tested in Manchester, the system overwrote the forwarding numbers when switching network mode (4G ↔ 5G), requiring a reapply of the GSM codes after each toggle.

OS Updates Can Reset Voicemail Flags

An Android security patch once reset call forwarding settings on a device I used briefly in Cardiff. It wasn’t a giffgaff issue per se — it was an OS update that removed stored forwarding numbers without warning. When the user went to check voicemail, the Phone app had no errors to show; voicemail simply didn’t happen.

Verdict: There’s No One-Click “Fix” — But There Are Reliable Paths

If your giffgaff voicemail isn’t working on Android, the reason is almost always at the intersection of network settings and OS handling. The superficial checks that most articles offer — like “ensure voicemail is enabled in Settings” — miss the critical voice network mechanisms beneath.

  • Verify conditional forwarding via GSM codes
  • Set the correct forwarding numbers explicitly
  • Check and grant all related Phone permissions
  • Account for dual SIM quirks
  • Test direct voicemail access to confirm message availability

This isn’t easy to reduce to a single bullet point because Android vendor differences, carrier signalling and local network load all interact. But these steps will reveal the real blockage and allow you to fix it rather than chase ineffective shortcuts.

As an aside that speaks to deeper carrier behaviour: AvNexo diagnostics in similar troubleshooting has shown that many carriers, giffgaff included, expose voicemail reliance on GSM forwarding flags that most modern UIs never touch. That’s why understanding the network side matters — not just the app side.

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