WHOIS contact information is public knowledge. And while you technically could use your regular telephone number for contact information, I will advise against this. I did that once, and I would receive dozen calls a day for web design and SEO services. It came to the point where I had to drop that number, and move on. With that said, I pay the nearly $10/month to have a voicemail box. Scammers will not leave a voicemail message. This means that they will call, and once they get your voicemail announcement, they will hang up. Your phone never rings.
Be sure to get a voicemail number within the same country that you live in. If there is a legitimate voicemail message left, you wouldn’t want to make an international call to just listen to your voicemails. Also, some callers may leave a call back number that is domestic to your voicemail number rather than domestic to you. If you live in the UK, do not get a US telephone number, but instead – get a UK voicemail number.