Why is it not possible to activate iPhone wi-fi calls in Italy?

This is not an apple limitation, it was a decision from the telecommunication companies not to support it, allegedly because of legislation making it more onerous for carriers due to the need to identify the caller that is more complicated through wifi calling.

I was able to use wifi calling in Italy with Italian wifi but an English number...

As of recently TIM and Wind both offer the option and very recently not just when on their wifi but on any wifi as long as you are in Italy (no wifi calling with an IT number abroad, US carriers allows this for example)

Hope this help!

Fra

I’m translating your post in case anyone else has a suggestion. But In my opinion, if your carrier does not offer Wi-Fi calling, there is nothing Apple can do about that. You can read more about it here:

Make calls using Wi-Fi on iPhone - Apple Support

Translation - first post:

Why is it not possible to activate wi-fi calls in Italy?

Translation - second post:

In Italy no company offers it, they say it's an Apple problem.

Wi-Fi calling is a feature that many cellular companies offer. Please contact your cellular carrier to see if they offer this service.

Contattaci - Supporto Apple ufficiale (IT)