How do I fix Wi-Fi calling issues on my iPhone with iOS 18.5?

Recommended Troubleshooting

1. Disable Wi-Fi Assist (if enabled):

• Go to Settings > Cellular
• Scroll down and turn off Wi-Fi Assist
• This prevents the phone from switching to weak cellular networks automatically, which can interfere with Wi-Fi calling in low/no coverage areas.

2. Toggle Wi-Fi Calling Off and Back On:

• Go to Settings > Phone > Wi-Fi Calling
• Turn Wi-Fi Calling off, wait 10 seconds, then turn it back on

3. Check Date & Time Settings:

• Go to Settings > General > Date & Time
• Ensure Set Automatically is enabled
• Incorrect time sync may cause call routing issues over Wi-Fi.

4. Confirm VoLTE and Carrier Settings:

• Go to Settings > Cellular > Cellular Data Options > Voice & Data
• Make sure VoLTE is enabled (if supported by your carrier)
• Some networks require VoLTE to properly route Wi-Fi calls.

5. Reinstall iOS via Finder/iTunes (optional advanced step):

If the issue persists, doing a clean install of iOS 18.5 via Finder (Mac) or iTunes (PC) may help resolve potential update-related software issues.

Final Steps:

If none of the above resolves the problem, I recommend contacting your mobile carrier to confirm that Wi-Fi Calling is properly provisioned for your account. There may be backend settings that need refreshing after device upgrades or iOS updates.

Additionally, I'd suggest reporting the bug to Apple via Apple Feedback, as this helps their engineering team investigate recurring issues affecting newer iOS versions.

So; I moved onto a newer iOS version as previously mentioned..

basically; I had to do a lot more research into how Wi-Fi calling works, and learnt this:

1) If your on Three UK network, your phone will be trying to connect to a DNS address of epdg.epc.mnc020.mcc234.pub.3gppnetwork.org (this the UK network specific address for Three WiFi/VOIP calling), so ensure this address resolves on that network correctly..

2) Also, relating to open ports Outbound from that network, WiFi calling needs the following open, in order to work properly: udp/500, udp/4500, udp/5060-5061, udp/40283-59999. Ensure these are not blocked outbound, otherwise negotiating the VOIP session with the 3gppnetwork.org endpoint will fail..

If it’s working on -some- WiFi networks, but not others the above is likely the cause, if not …. try what I -elduded- to in my previous posts, my WiFi calling is working perfectly since doing that..

Hope the above helps 👍

Hi. My wife's phone suddenly stopped working with wifi calling. I complained to O2 who said it was Apple and they had no issues with wifi calling. Eventually after resetting everything I swapped out her O2 sim for my Vodafone sim and wifi calling worked fine on her phone. I then phoned O2 again and they sorted it. It was obviously the network carrier's fault (O2).

I believe this to be bug in iOS 18.5; as it was resolved when running a “newer” iOS….

i tried every one of the steps mentioned, checked with my carrier (they said they don’t block it) and tried on a non Apple device (this worked fine), weirdly the problem didn’t exist in 18.0 but rolling back obviously isn’t possible..

Ok, I guess we will agree to disagree.

On my iPhone 15 Pro Max, on Three UK network, WiFi calling was not working after iOS 18.2… continued up to latest stable iOS 18.5.

I checked with my carrier, they do not restrict WiFi calling for any users, upon upgrading to the latest non-stable version of the OS, the problem is gone, I have also tested this on an older iPhone (iPhone 14 Pro running iOS 18.5), this didn’t work with same sim and different sim (all on Three UK), but the same sims all worked on a non-apple device without issue, pointing out it’s not contract/tariff/carrier related.

WiFi calling is essentially a standard and is basically VoiP, usually using endpoints from the 3gppnetwork in most countries, so the differences between apple and android implementation are negligible….

i hope this helps someone in a similar situation.

I’m having identical issues since 18.5 and have even changed phones and it still hasn’t worked since the iOS previous to 18.5. It’s not a carrier issue.

PS: I used to work as a dev for Apple, I’m not guessing, I’m explaining that they’re correct.

[Edited by Moderator]

WiFi calling is tied to your cellular service. If you have a new iPhone 16 pro and you have transferred your cellular service to that device, I would not expect your iPhone 12 to be able to use WiFi calling. WiFi calling requires that the device actually have a cellular service plan , which your 12 does not.

It’s not all about cellular service. I know these phones like the back of my own hand. Also I think you replied to the wrong person. I have a 16 pro and wifi calling worked fine up until 18.5. There are hundreds complaining of the same thing. I used to work for apple. There is a connectivity bug and bugs don’t always affect everyone with an iPhone.

Experiencing somewhat similar issues— 3UK, iOS18.6, WiFi calling kicks in when cellular reception is poor, I can tell from the "WiFi Call" logo. On some Wi-Fi networks - no issue whatsoever, on eduroam at work WiFi calling almost never works. Work IT and 3UK keep pointing fingers at each other and Apple...

18.6 which is doing the same thing on our network. We still have iPhone 7s running IOS 15 and they work fine. We have just moved to 3 UK and this is when the issue started happening so there is no rhyme nor reason to it.

So it wasn't a problem with the "newer" versions of iOS, was it? The carrier tech support staff are usually lazy, and they tend to blame Apple for everything under the sun, when it reality it is their "fault" either by changing or not applying the correct "standard".

A while back Spectrum (an ISP) with Apple Mail was unable to fetch email, because they changed the server configuration, and guess what tech support at Spectrum did: blame Apple.

Ok, so I genuinely think something has changed between the stable and not-so-stable iOS imho.. regarding how the network stack behaves, I’m going to do some wireshark captures to see what I can see between the “latest stable” and not-so-stable..

something has definitely changed as to how it determines whether to use WiFi calling or not, and the logic around network selection, mines still working splendidly , but I’m going to dig into it a bit more as I’m intrigued now I’m hearing about more people with the issue..

They said they do not block anything… like I said; I’ve reinstalled iOS 18.6 on my phone and WiFi calling never works; it says I need WiFi/cellular signal in order for it to work (WiFi is connected at this point), I move back to unstable dev iOS, and it works without fault… it’s related to the way the networking stack is implemented or related to how stringent to the standards around VOIP, the newer (non-stable) IOS works flawlessly every time..

If the implementation of the stack is up to standards in the new version of iOS, and Wifi calling works on most networks, then it is up to 3 to get on the bus, and make the changes, and not to expect Apple to downgrade their implementation.

Three offers terrible customer service. Their staff at a store were clueless a year ago on how to transfer a pay as you go physical SIM to an eSIM.

Eventually the option was available on the phone itself without having to go to store. No wonder they merged with Vodafone.

Since WiFi calling is a carrier feature and managed by them, I suggest you contact your carrier to try and sort the problem.