Enabling Voice-Over-WiFi on the OnePlus 5T and Three UK

My mobile provider - Three UK - offers WiFi calling, but only if you have a phone purchased directly from them. For everyone else, they have a crappy app which hasn't been updated in two years.

So, let's break out of their artificial restrictions and get some WiFi calling on the OnePlus 5T!


  1. Open your phone dialler app.
  2. Dial *#800#
    Dialler screen.
  3. You don't need to press send, you should automatically be taken to this engineering menu
    Log Test menu screen.
  4. Touch the top menu item "oneplus Logkit"
  5. Scroll to the bottom
    Log Menu screen.
  6. Press "Function Switch"
  7. Select "VoWifi switch"
    VoWifi Switch.
  8. Your phone will ask to reboot - so press OK to reboot
  9. Once the phone has restarted, go to your Settings menu
    Android settings menu.
  10. Select "SIM & network"
  11. Scroll down and select "Wi-Fi calling"
    Use WiFi Calling switch.
  12. You can optionally switch the "Calling preference" to "Wi-Fi preferred". If you do that, calls will go via Wifi even if you have a mobile signal.

Test it!

Put your phone into Aeroplane mode, then switch on WiFi. You should see this logo at the top of your screen.

VoWifi Logo on the top of the Android display.

Try to make a call.

It doesn't work??!

If this doesn't work for you... sorry! You should speak to your network provider to see what they recommend.

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4 thoughts on “Enabling Voice-Over-WiFi on the OnePlus 5T and Three UK

  1. This is outstanding, and exactly what I was after. Thank you for putting this on your blog :o)



  2. If VoWiFi works, and the handset does VoLTE on networks that support it, you want to turn VoLTE on, too - assuming that the handset and network actually implement the standards properly, support for VoLTE will give you seamless call hand-off between WiFi and 4G (LTE) mobile networks, plus calling on 4G with seamless fallback to 3G/2G as appropriate (and fall-forward to 4G when in coverage), plus audibly glitchy handoff between WiFi and 3G/2G networks.

    On its own, this gives you better chances of sustaining a voice call; further, there's optional components to the spec that, if implemented at both ends, will give you seamless handoff between WiFi and 3G networks for voice calls, meaning that you can keep a voice call going until you lose coverage.

    For the nerds among us; VoWiFi and VoLTE are the same thing on different radio networks (both are SIP + RTP talking to the network operator's IMS service). In VoLTE, the IP packets are carried over LTE directly to your network; in VoWiFi, your phone establishes an IPSec tunnel to a well-known DNS name (epdg.epc.mncXXX.mccYYY.pub.3gppnetwork.org, where XXX is the three digit MNC, add a leading zero if you have a 2 digit MNC like 30, and YYY is the MCC, such as 234 for the UK).

    There's specified handovers to cleanly (no glitches) hand over the IP packets between radio types, and to switch from IP to circuit-switched voice if on the mobile network. There's also specified hand overs for IP to circuit-switched if not carrying IP over the mobile network (which are allowed to glitch), and an optional spec for carrying the IP packets over UMTS/HSPA instead of LTE.

  3. Hi, I just read your article and want to thank you for the kind and intuitive way you have kindly shared this information. However i have also found a potential bug / artefact.

    If like me you have 2 sims, and your primary sim is say Vodafone the Wifi Calling does not work. Wifi Calling only applies to the primary SIM it seems to me which is a shame.

  4. hi will this also work on the three UK network or could there be some other thing blocking vowifi thanks.

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