So, apparently dialing *67 at the beginning of a phone call has the effect of making that call anonymous, hiding your Caller ID. But how exactly does that work, and is it some sketchy third-party service that is doing the hiding for you?
It’s the phone company that does the blocking. *67 is for per call blocking but you can arrange for a complete block on the line and then must dial *82 ( I think) to unblock a particular call
According to this site it may not work for all phones, but there are other ways for phones that are exempt:
Yep. My phone is set up to block my caller ID for every call I make. My contact list is set up to dial *82-xxx-xxx-xxxx for every contact’s number, since they know my number already.
To add more detail, *67 blocks CID but not Automatic Number Identification (ANI) which is passed between the exchanges and phone companies for billing and audit purposes. ANI is never passed to the callee.
And even if you block your out-going caller ID, you still cannot block it when calling 911 and perhaps certain other magic numbers.
I think it is passed to the operators of 800 and other toll-free lines as they are paying for the call and it should be on their bill.