My doctor's office is in my phone book, so that's covered.

For things like restaurants, I know that I'll be receiving a call from an unknown number and will just answer it.

For unexpected things, like Uber, they'll leave a message on my voice mail. I'll be notified of that as soon as they're done and will check it immediately.

That all works for me. It's a shame that I have to do all of that rather than just answer the phone, but there's no other option that I can see.