Issues receiving a scheduled callback from Apple Support

When Apple does a scheduled callback, it never rings the phone. I get an email saying that they tried to call me but I didn't answer.

I do _not_ have Silence Unknown Callers turned on. However, I have received several calls in the past month from people pretending to be Apple Support who are actually spammers. I may have blocked those numbers.

When I click on the link to request a call, I _do_ get the call, but that comes in on the 512/884-5022 number. I was told by several Apple representatives that callbacks can come from several numbers, not necessarily the 800/275-2273 number. However, they say they don't know or can't release the numbers the calls will come from. Without that, I don't know which blocked numbers to unblock.