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? How can I get equivalent functionality of ADB for iOS?
No, Apple does not expose the ability to place phone calls to third party apps. They specifically block all such access from third party apps. You would need to build a rig that operated the screen like a user, which would not be easy or very reliable.