The service works like this:

* I  grab my cell phone (123-456-7890) and call my doctor/dentist/medical office

* It's after hours and they are busy with other calls

* Their phone system turns around and forwards my call to a 3rd-party number (say 111-222-3333) emitting my Caller ID info ("Aaron" <1234567890>)

* They see a call come in on 111-222-3333 and know it's for "Dr. Bob's Office", so their system accesses his patient database and looks for my patient record with the phone number 123-456-7890 and someone answers the call saying "Thanks for calling Dr. Bob's office".

My understanding is the ability to spoof Caller ID info across the PSTN is going away.

I tested, and I certainly can't do it with a Twilio SIP trunk.

The main reason I'm curious is I have a customer that has their own phone system that I help them manage (FreePBX linked to Twilio).  They just purchased an office that uses a 3rd-party phone provider (Weave) along with this 3rd-party answering service, and they are somewhat upset that I can't make it work with their existing phone system.  The third-party answering service doesn't have any way of interconnecting other than spoofing Caller ID over the PSTN to a random number they assigned to the medical office.

Are services like this going the way of the dodo?  Are they having to set up private SIP trunks between clients to get this functionality?  Do some VoIP providers allow you to spoof Caller ID for this purpose under some sort of agreement?

Thanks,

-A