If you are ever required to give a phone number but don't want to then you can use an official fictional one. This means no-one else will have access to it (or be annoyed by it). Same with email addresses.

If you need access then you could use https://smsprivacy.org or https://dtmf.io. I've not tried these though. Or of course you could build something yourself with https://www.twilio.com or https://www.nexmo.com.

I wrote a bit about this here: https://unop.uk/phone-numbers-for-examples-and-user-identifi...