As others have alluded, there are unknown third parties who must call you (and you would want their call). For example, the hospital: something has happened with a loved one. We can probably solve this problem with certification. Show me your medical license (or hospital scale equivalent) and you get to make unsolicited calls. Then we allow people to select certified unsolicited calls by category: medical, financial, civic, etc.
Even in this case, I'd rather get a text message. A mere call doesn't provide any context and is not informative. Maybe your loved one showed up in their ER or maybe it's a billing issue.
The text message should explain the nature of the call and which number to call in reply.
I agree that a text can help provide context, and I definitely prefer it for non-emergency communications, but sometimes people want to go straight to synchronous communication so they can discuss urgent details without delay.
> The text message should explain the nature of the call and which number to call in reply.
You lost me here. If I get an unsolicited text message claiming to be a doctor who needs to speak to me urgently about a loved one's medical emergency, I'm not calling back via any number other than the hospital's front desk or switchboard. Invoking an emergency and asking you to call an unverified phone number is scamming 101.
I think there are HIPAA issues there. You can't just SMS a random number medical information, it ends up being something like "$HOSPITAL has a message for you, log in at $RANDOM_EHR or call us back at $NUMBER".
