At my side not even VoLTE is working. I think VoLTE and VoWIFI problems are connected.

I have AT&T. I performed the following steps:

  1. Settings > Network & internet > SIMs > Wi-Fi calling > Use Wi-Fi Calling [on]
  2. Settings > Network & internet > SIMs > Wi-Fi calling > Use Wi-Fi Calling > Calling preference > Call over Wi-Fi
  3. Shortcuts (from a pull down) > Internet > AT&T > [turned cell service off]
  4. I called my son without issue.

I think it's a carrier issue, not GrapheneOS.

    dcd-graphenediscuss I don't have "WI-Fi calling" option in my SIMs menu, but I know for a fact that my carrier have this feature. (Works VoLTE and VoWIFI perfectly with he same SIM on my Huawei Mate 20 Pro phone)

      dcd-graphenediscuss

      I did step 1, but I cannot find the settings for step 2.
      Wifi Calling did work with the same SIM card and my previous phone (oneplus 6)

        Zoltan have you dialed *#*#4636#*#* and checked Phone Info to see what is provisioned or not, inclusive of WiFi Calling?

          dcd-graphenediscuss I just did the same test and, after disabling mobile data .... was able to make a call as well as receive and answer a call.... Hmm, this means that WiFi is working
          I'm on Verizon.
          My assumption posting upthread about WiFi calling not working was the fact that my phone constantly misses and drops calls as well as "Voice over WiFi: Unavailable" under "IMS Status" in the testing menu screen. I guess, I need to look deeper into this ...
          Would aforementioned test I did be a conclusive way to test WiFi calling or is there anything else I could test?

            f13a-6c3a nothing else to test, if you can make standard telephony calls via wifi using the stock dialer app then wifi calling is active.

            Different carriers have different thresholds for what causes wifi calling to 'kick in'. It can depend both on what your cellular strength is at as well as your WiFi strength/quality.

            MetropleX I can't turn on the "VoLTE provisioned" and other functions. They're all grey. Is this a bug?

              The proper way of testing Wifi Calling is to enable Airplane Mode, then only turn on Wifi and make a call. The dialer app should display a Wifi icon or text indicating that it is a Wifi call but this varies between carriers.
              Turning off the cellular toggle from the Internet quick tile does NOT force a Wifi call and it doesn't prevent you from making standard cellular calls.

                shorty Yeahh, you see, when I do that (Airplane mode on, then turn WiFi on) - I can NOT make a call nor I can receive one, I get "Turn off airplane mode or connect to a wireless network to make a call". Tried waiting for a while thinking maybe WiFi Calling need some time to "link up" - no go.

                I feel like test during which you only turn off mobile data is false as it might, I suspect, keep the cellular connection going. The airplane on test is re-confirms what I was actually experiencing.

                  Zoltan these toggles are not meant to be interacted with by users. These toggles are changed remotely by your carrier when they provision them and send the info to your device.

                  Seek your carriers instructions on VoLTE and VoWiFi and follow them, if you do and still have issues return here for advice tagging me.

                    MetropleX I talked with my carrier support. The guy on the phone said:"Your Phone maker needs to allow and support your connection on VoLTE or VoWIFI" What's this bullshit, is it possible that until Goggle is not allowing my carrier/me to use VoLTE or VoWIFI I can't use it?

                      f13a-6c3a
                      Yes, as long as you are logged into the mobile network, you can make calls via GSM/VoLTE. Internet access is not required for this.

                      You can only be sure that VoWifi works if you can make calls with airplane mode and Wifi turned on.

                      VoLTE works for me, but not VoWifi.
                      In the Test Menu (##4636##), I can see "Wifi Calls set up" is checked.

                        Zoltan Beerman have you both read and followed the directions as laid out here in our documentation:

                        https://grapheneos.org/usage#carrier-functionality

                        Please do and report back, same for anyone else with issues and when doing so please mention the following:

                        Carrier:
                        Carrier Settings (SETTINGS>NETWORK AND INTERNET>SIMS):
                        Does your carrier list your device as supported? Y/N + Link to Carrier Page
                        WiFi Calling Option Visible? (SETTINGS>NETWORK AND INTERNET>SIMS): Y/N
                        State of Provisioning Toggles (*#*#4636#*#*): VoWiFi On/Off and VoLTE On/Off
                        Have you Reset Mobile Network settings? (Settings>System>Reset options>Reset Wi-Fi, mobile & Bluetooth>Rebooted?): Y/N

                        Thanks

                          MetropleX Carrier Settings (SETTINGS>NETWORK AND INTERNET>SIMS):

                          Telekom.de

                          Does your carrier list your device as supported?

                          Y (They do not have a List, they only say it must be supported by the phone)
                          https://www.telekom.de/hilfe/mobilfunk/telefonieren-sms-mms/wlan-call/voraussetzungen

                          WiFi Calling Option Visible?

                          Y
                          (But only "Settings > Network & internet > SIMs > Wi-Fi calling > Use Wi-Fi Calling" -> Enabled
                          I donΒ΄t see "Settings > Network & internet > SIMs > Wi-Fi calling > Use Wi-Fi Calling > Calling preference")

                          State of Provisioning Toggles (##4636##):

                          VoLTE On
                          VoWiFi On
                          (Switch to the right, both grey)

                          Have you Reset Mobile Network settings?

                          Y
                          (Nothing has changed.)