Once your number gets on a list of known valid numbers it is sold to every telemarketing company in the world, and there are lots. They use all sorts of automation like autodialed recorded messages. There is no way to stop it and no way to get off the list once you are on it.

I would suggest you get a new number but only use it for making calls. Use the old number for 2 factor authentication and web site registrations. That way you only use the old number when you need to access on line banking or to get access to secure websites. Don't use it to make or take calls just for SMS codes for site authentication.

I worked for a company that offered VOIP services and we used to hand out hundreds of numbers to telemarketers and the phone call costs were unbelievably cheap. It cost them nothing to get another 100 numbers every few months. They call from Sydney but the calls get routed so that they always look like a local number or at least the same country. Businesses can appear more multinational that way. Makes it look like they have offices all over the world, when its just a couple of guys in a garage somewhere.

Believe me two numbers will be so much less trouble just as long as you never give out the number you use for making calls. Only ever give out the other number if you have to.

I’ve been getting a few calls lately, from different numbers.
No message left and the numbers don’t appear on any lists like this.