I've recently had a tough time getting WiFi calling working at our property in France, on a Vodafone PAYG phone, and wanted to pass on some tips as to how I eventually got it working after months of failed attempts and frustration.
This is an older iPhone 6S, running current iOS 15, although I don't feel the age of the phone or OS is particularly relevant. Note that this is a PAYG phone on the ultra basic 'Pay as you go 1' plan, so not 'Red' or 'Business'.
Firstly, I was told that it is not possible to enable WiFi calling on such a basic PAYG plan, and Internet research suggested this was the case, including from Vodafone's own webpages on the matter. Nonetheless, I was able to have it added to my plan very easily, by speaking to the 'right person' at Vodafone customer service, with no questions asked. Two earlier people I spoke to at Vodafone said it was not possible. Perhaps those people were reading off the same inaccurate, or out of date webpages.
Secondly, I was not able to get it enabled the 'first time' while I was in France, it seemed I needed to be in the UK for this, but read on for the whole story... as this theory may actually be a red herring.
The story
The option to enable WiFi calling was always in my iPhone settings, that wasn't ever the problem (I had my Vodafone APN / phone settings installed correctly on the phone), but something else seemed to be preventing it from enabling. I tried to enable it several times while in France, but nothing ever got it working.
This was hugely frustrating as I have an identical phone from a different cellular provider, and WiFi calling enables perfectly and easily every time.
I had actually given up on ever getting it working with Vodafone, but interestingly, one day, as soon as I had returned to the UK and was on a WiFi network, WiFi calling enabled!
When I returned to France, it also worked!
I can't be sure that getting it to work in the UK 'first' was the key to it working abroad, although it might be. It may simply have been the circumstances under which I was trying to enable it abroad. The following experience may contain the answer...
One day, my WiFi calling stopped working in France, and identical to my earlier struggles there seemed to be nothing I could do to re-enable it. I literally started thinking I would have to return to the UK to have any hope of it working again, and was annoyed at myself for disabling WiFi Calling and re-enabling it.
I then found a way to reliably re-enable it while abroad. I suggest this process could be tried by people before jumping to any conclusion that being in the UK is actually needed to get it working the first time. Again, at the risk of repeating myself, that may be a total red herring. Also note that this process is likely a good process for anyone trying to get WiFi calling working - wherever you happen to be.
What worked for me
1. Turn off WiFi Calling in iPhone settings
2. Disable WiFi on the phone
3. Make sure you have a decent cellular signal, and cellular data is working (I was on 4G, but 3G should in theory work). In my case I was on the SFR network in France with roaming enabled.
4. Enable WiFi Calling in iPhone settings and wait for about 1 minute. Nothing will show on screen.
5. Now turn on Airplane Mode
6. Now enable WiFi on the phone and connect to a good WiFi connection
7. Wait for a couple of minutes to see if WiFi calling shows up
This worked for me, and is the only sequence I've been able to use to get WiFi Calling enabled reliably while abroad, where it wasn't enabled previously. Once enabled, as others have said, it's best to be in airplane mode generally to stop the phone trying to connect to a weak cellular network.
I hope this helps someone else. If anyone has experience enabling WiFi calling for the first time while abroad, it would be great to see those stories too.
