How did you do this
These are the steps we took:
1. Get a twilio number
2. All incoming phone calls to the home phone are redirected to that twilio number [1]
3. If incoming number == grandma, request from an api endpoint the next relative to dial. Redirect her call to them.
4. If no one is available, play the voice mail
5. If incoming number != grandma, redirect the call to dad's mobile number [2]
[1] A child comment by macNchz noted correctly about "Selective Call Forwarding". This would have simplified the process and we could have skipped step 5, but our telephone provider did not offer it.
[2] Note that this is a bit of a compromise in the setup. The home phone never rings anymore and all non-grandma calls go to dad's cell. But they were happy to accept this.
I never knew about ATA's! I think would have solved things a little more elegantly. Thanks!
In our case, my grandmother always calls my parents home phone number. The phone provider only offers simple call forwarding, so we route all calls to the home phone over to a Twilio number. We have a very simple Twilio Studio flow that routes calls from my grandmother's phone number to the call handler script we created, and all other calls are routed to my dad's cell phone number: https://share.cleanshot.com/ywwhzJ8H
We are a little lucky in that we can forward calls from our landline to a cell phone. If your relative is calling you directly on your cell phone, your carrier would need to offer selective forwarding for this strategy to work