Why does my iPhone 16 cut off outgoing calls after one ring?

Are you saying that the call fails? Does this happen to all calls? If that is the case, first thing to try is to Force Restart the iPhone and try again. Force restart iPhone - Apple Support If that does not make a change, then contact your cellular carrier. They are responsible for call handling.

I would contact your carrier and see if there is an issue with your device on their network. Since the SIM works in another device and nothing works in yours, it may be an issue with how your account is configured. Work with them to troubleshoot this as they are responsible for call handling.

Try the troubleshooting steps I provided.