You can't remove the Phone app from an iPad in iPadOS 26. Even when the iPad in question has no cellular functionality. The best you can do is remove the icon, but you get a dialog telling you it won't be removed.

Which is stupid as I don't want my iPad to be getting every voice mail and imessage and so on that my phone does. They are different devices and serve different purposes. My iPad is totally a media consumption device and I have no interest in it being integrated into my phone's communication functions.