[nonameiguess]

Most delivery services with an app have messaging built-in so you don't need to rely on calls, but I also know when I'm expecting a delivery or a driver to pick me up, and if an unknown call comes from my area code (the one I'm actually in, not the one my phone number is in), I'll answer that. It's pretty easy to distinguish between times I might expect a call and all other times.

For all those other things, though, I'm not sure why you need to answer unknown numbers. I've never owned my own business, but did manage a small business and we had dedicated business lines. No one needed to call my personal phone. For buying and selling real estate, there are agents that act as go-betweens and you can put their number on your contacts list. For renting, put the management company on your contacts list.

[reaperducer]

Most delivery services with an app have messaging built-in so you don't need to rely on calls

I've used dozens and dozens of delivery companies over the years, and the only delivery company I've found that doesn't have its people calling on phones is DoorDash, and even that uses SMS. Plus, most of the best places don't use services, they have their own people.

we had dedicated business lines

Doesn't help you when someone needs to contact you in an emergency, like the alarm company, or the landlord, or security, or the police, thousand other things.

For buying and selling real estate, there are agents that act as go-betweens and you can put their number on your contacts list.

Sounds good in theory, but doesn't work in practice. There can be dozens and dozens of people and companies involved in such a transaction, and you can't predict who they all are.

For renting, put the management company on your contacts list.

When the management company sends a vendor over to fix something, you don't know what number they'll call from.

To "never" get an unexpected, important call sounds like a side effect of a quiet life. I envy you.