[simulate]

All phones have undeletable apps provided by their manufacturers. For example, on iPhones you cannot delete Messages, Phone, Safari, Clock, Photos, Health, App Store, and Camera in a conventional way.

[reaperducer]

Phone

Not much of a phone without a phone app.

But Apple does sell an iPhone without a Phone app. It's called an iPod.

[Rebelgecko]

Does iOS not support 3rd party dialer and SMS apps?

[ryandrake]

It does not. Just things like Skype, WhatsApp, etc.