honestly, this responses just pisses me off.
not everyone who needs to be careful with their privacy is fortunate to have a stockpile of money to spend on carriers that are WAY more expensive than they need to be. or reliable internet access.
i understand that you may not have an answer to the original question of "how do I ?", and you have the opportunity to avoid the situation in the whole and not have to think about it -- that's pretty awesome! but it completely ignores the fact that everyone is in a different situation, with specific and unique needs and context. it reeks of being patronizing tbh.
we don't know what this person's situation is, so the thing to do here is to take them at their word and help them with the problem in front of us. suggestions towards alternative solutions are of course welcome, but things like "not sure why youd want to do that" only serves to show that you don't understand the situation.
not everyone has the same choices available to them in their situations, everyone's threat model is different.
oof yeah :| Twilio has pretty much made half a business model out of promising that you can refuse VoIP numbers using their APIs soo it's a real thing