I know this is a little off topic for saynoto0870 but there's a good bit of telecoms expertise here.

I have a Samsung Galaxy S8, bought outright from a phone supplier. I also have a very good SIM only deal from Three. (£8/month for unlimited everything. Still don't quite know how it happened. I didn't ask for it, they just gave it to me). Until recently I used a Three app called "3 in touch" to use telephony and texts over wifi. Very handy in places with bad mobile network connectivity. A few months ago 3 discontinued the app but said that most newer phones could do all this inherently. My S8 is in that category but the relevant menu option was missing. I have ensured that my handset is fully updated - both Android and the standard phone app.

I contacted 3 and explained my problem. They said they only offer this service on handsetss that they have supplied and that they can't update my software to do it.

I've been escalating my complaint and they've offered several months free as a compensation but are unable to explain why enabling wifi calling should be such a problem.

I don't really want to leave 3 (see great deal above), and in any case I may not get wifi calling on any other network either.

Any thoughts?

What you've siad is useful. Assuming you didn't get the phone itself from Three (or did you?) it shows that a generic modern Android phone can do calling over wifi on Three.

Actually the "3 in touch" app wasn't very well integrated with normal network phone/text so probably a good thing it's gone. But really ought to be able to make calls over wifi as standard without hassle on a modern phone.