Journalists could have two sims, one with which they call people when they need to say who they are and one elf r when they don't need to say who they are.
But that sim would only last until the person they call tags them using the service.
That being said, I'm not sure why this is changes anything for reporters. People can already put a phone number online or share it with the government. The same precautions they would need to take without this service would still be valid.
