Xiaomi WiFi Calling Missing on O2 Devices in the UK

Xiaomi WiFi Calling Missing on O2 UK – Fix

If you can't find the WiFi Calling (VoWiFi) option on your Xiaomi, Redmi, or POCO device with an O2 SIM, this guide explains why and how to fix it. The issue usually isn't a fault with your phone—it's often a hidden carrier check that needs to be disabled.

Quick Answer:
If WiFi Calling is missing on O2, first dial *#*#869434#*#* in the Phone app. If it works, you'll see a message saying "VoWiFi carrier check was disabled." Restart your phone, then go to Settings → SIM cards & mobile networks → O2 SIM → WiFi Calling should now appear. If the option is still missing, contact O2 to confirm WiFi Calling (VoWiFi) is enabled on your account and ask them to refresh your SIM or eSIM profile.

🔍 Quick Diagnostic Table

What you seeWhat it usually means
WiFi Calling toggle completely missingHidden carrier check re-enabled or device compatibility/carrier configuration
WiFi Calling toggle greyed outO2 hasn't provisioned VoWiFi on your account
WiFi Calling option missing only on one SIMDual SIM configuration or slot issue
WiFi Calling works but disconnectsAdGuard, VPN, or battery optimisation interfering

Why O2 WiFi Calling May Be Missing on Xiaomi

O2 supports WiFi Calling on many Xiaomi devices. However, several factors can hide or block it:

  • Hidden carrier compatibility check – Xiaomi devices use a hidden check that can hide WiFi Calling for carriers not on an approved list. This can become enabled again after a software update or other system change.
  • Device compatibility or carrier configuration – O2's official support pages list specific Xiaomi models, but many other devices work with the hidden code. MVNOs like Giffgaff may have different compatibility.
  • Carrier provisioning – O2 may not have enabled VoWiFi on your account or SIM profile. This can happen after a SIM reprovision, account change, or carrier-side update.
  • App conflicts – AdGuard and other VPNs can interfere with IMS registration, preventing WiFi Calling from connecting or registering correctly. For some users, temporarily disabling AdGuard resolves the issue.

Fix 1 – Disable the Hidden Carrier Check

For many Xiaomi devices, this is the first fix worth trying.

Try this first:

  1. Dial the hidden code – Open the Phone app and dial *#*#869434#*#*. If the code works, you will see "VoWiFi carrier check was disabled" or "VoWiFi carrier check is disabled".
  2. Restart your phone – After dialling the code, restart your device.
  3. Check the toggle – Settings → SIM cards & mobile networks → O2 SIM → WiFi Calling should now appear.
  4. If the toggle is still missing, dial *#*#86583#*#* as well (this enables VoLTE, which can sometimes help with VoWiFi registration).

Note: This code works on many Xiaomi devices but may not work on all models or HyperOS versions. If nothing happens, your device may not support this code.

Fix 2 – Check O2 VoWiFi Provisioning

If the toggle is greyed out or still missing after the hidden code, O2 may not have enabled WiFi Calling on your account.

Try these in order:

  1. Restart your phone – A simple reboot can sometimes refresh the connection.
  2. Toggle Airplane mode – ON for 30 seconds, then OFF. This often prompts the phone to re-register with the IMS service.
  3. Check mobile data is enabled – IMS registration on many UK networks requires mobile data to be switched on, even while you're connected to WiFi.
  4. Check your account – Call O2 (202) or use the O2 app. Ask: "Is WiFi Calling enabled on my account? Can you refresh my SIM profile?"
  5. Check SIM age – If you're using an older SIM that predates O2's WiFi Calling rollout, your carrier may recommend a replacement SIM.

Fix 3 – Check for App Conflicts (AdGuard, VPN)

Some users have reported that AdGuard and other VPNs prevent WiFi Calling from activating on O2 networks.

Try these in order:

  1. Disable AdGuard or any ad-blocker temporarily – Some ad-blockers prevent WiFi Calling from activating, especially when reconnecting to WiFi.
  2. Disable VPN – If you're using a VPN, try turning it off and reconnecting to WiFi.
  3. Restart your phone – After disabling these apps, restart and check if WiFi Calling reappears.
  4. Test with a different WiFi network – If the issue only occurs on one network, the problem may be network-related.

Fix 4 – Check Dual SIM Configuration

If WiFi Calling is missing on only one SIM, the issue is likely dual SIM configuration or slot.

Try these in order:

  1. Check which SIM is selected for mobile data – Settings → SIM cards & mobile networks → Default for mobile data. On some Xiaomi models, IMS and WiFi Calling status depends on the SIM used for mobile data.
  2. Swap SIM slots – Power off → move the O2 SIM to the other slot → power on → check if WiFi Calling appears.
  3. Set O2 as default for calls – Settings → SIM cards & mobile networks → Default for calls → Select O2.
  4. Disable the second SIM temporarily – Settings → SIM cards & mobile networks → Turn off the second SIM → restart → check if WiFi Calling appears.

Fix 5 – Check After a HyperOS Update

HyperOS updates can sometimes reset network settings or restore Xiaomi's default carrier compatibility check, which may cause the WiFi Calling option to disappear on some devices.

Try these in order:

  1. Run the hidden code again – See Fix 1.
  2. Restart your phone – After running the code, restart before checking if the WiFi Calling option has returned.
  3. Check preferred network type – Settings → SIM cards & mobile networks → O2 SIM → Preferred network type → set to 5G/4G/3G auto.
  4. Reset network settings – Settings → Connection & sharing → Reset Wi-Fi, mobile networks, and Bluetooth (last resort – removes saved Wi-Fi passwords).

eSIM Users

If you use an eSIM instead of a physical SIM, ask O2 to refresh or reissue your eSIM profile if WiFi Calling suddenly disappears. In some cases, downloading a new eSIM profile restores IMS registration and WiFi Calling.

Quick Questions

Why is WiFi Calling missing on my Xiaomi O2?
Most commonly, Xiaomi's hidden carrier compatibility check became enabled again after a software update or other system change. Dial *#*#869434#*#* and restart to restore it on many devices.

Does O2 support WiFi Calling on Xiaomi?
Yes, O2 supports WiFi Calling on many Xiaomi devices. You may need to use the hidden code *#*#869434#*#* to enable it on some models.

Can AdGuard or VPN stop WiFi Calling from working?
Yes. Some ad-blockers and VPNs can interfere with IMS registration, preventing WiFi Calling from connecting or registering correctly.

What if WiFi Calling is greyed out?
Your carrier may not have enabled it on your account. Call O2 to refresh your SIM profile or network provisioning.

Why does WiFi Calling disappear after every update?
Some HyperOS updates can restore the default carrier compatibility check, meaning you may need to run the hidden code again if your device supports it.

Can I use WiFi Calling on O2 without VoLTE?
On many Xiaomi devices, WiFi Calling depends on IMS services. Enabling VoLTE and WiFi Calling together often provides the most reliable registration.

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