Spam callers can get your number from a variety of sources. This may include warranty cards, online shopping accounts, social media accounts, public records, data brokers and people search sites, and data leaks and breaches.  You can reduce the exposure of your phone number and other contact details by removing your data from the data brokers and people search sites that sell them to marketers and other third parties (even scammers, on occasion). You can also try an automated data removal service like Incogni to keep your personal information off the market.