Phone carriers are local, and there’s not really much of a choice. No carrier is “safe” concerning privacy, because of the way they work.
You should also avoid conventional SMS/phone calls if you value privacy, because they’re super easy to tap into (therefore opting for secure and private messengers and VOIP call providers).
Just go with the one that seems the most professional (certainly not WindTre). In Italy we don’t have the big data espionage other countries are subject to, however if you want to, use a VPN (ProtonVPN is good even free if you don’t want to spend).
As for phone browser, Firefox is a thing and works really well, but doesn’t have nearly the same flexibility and attention to detail that the desktop experience has (no about:config, a handful of extensions). For maximum privacy, Tor can be used on Android too (at the cost of most websites’ functionality).