iOS native-layer automation

I need to automate iPhones (6s) that are in a radiated screen room to place VoLTE calls to each other. I have already done this with Android, I set a laptop in the screen room and connect the Android phones via USB and then run scripts from the command line using ADB which automates the native-layer on the phones. I need similar capability for iPhones. Apple says no solution exists. I have looked into other software (Ranorex, TestPlant, Conflair, etc.) but they cannot meet my needs as they are unable to access or automate the native-layer, only the application-layer. But I am not trying to automate an app, I need to automate the phones.

I would prefer not to jail break, and my iPhones need to be running the latest iOS version. So, is it possible? Is there a software that has escaped my searching that can do this? How can I get equivalent functionality of ADB for iOS?