The problem with these calls is that some of them are genuinely legit competitions. I got a call asking for raffle tickets from a charity I regularly donate to. I couldn’t understand why they were asking me questions that I thought they should already have on file. I said I’d call them back. I checked my legitimate mailings from this charity & the phone number was different. I called their toll free number, by now I was convinced that the first caller was a scammer. I found out the raffle was genuine, to my surprise. They didn’t have my details because their policy is not to store customer info. The woman on the phone laughed then transferred me back to the first caller. They had different numbers yet they were all the same charity.
Your details can be sold to companies promoting anything. They can be legit companies or they can be scams. You can get yourself put on a “Do not call” list.
https://www.donotcall.gov.au
If you ask to call them back, you can check the phone number online at a reverse phone number website, but some numbers have scant details.