TweetUnfortunately, these calls are becoming increasingly sophisticated, and it's harder to stop them. I've heard of some companies selling databases with phone numbers and then using them for targeted advertising and sales calls. It's not fair or legal, but it's hard to stop it from happening.
You can use a free number for verification. This method gives you a temporary number that you can use for online verification and sign-ups. You can keep your personal number private and still receive important calls.
Also, you can contact your phone provider and ask them if they can do anything to block these calls for you.