How in the world are they getting personal information?

It’s my birthday, and I received a message from a cult that I have never signed up for. The message suggested that I "uniquely celebrate my birthday by donating to feed the homeless" or something along those lines. My concern is how they obtained my personal information. My contact number is only shared with a few people, and I haven’t used it for any sign-ups or anything similar. I’ve never visited any ISKCON center or provided any personal details, so I’m concerned about how they have my information. It might not seem like a bigger problem, but the telephonic companies make it public our personal details like date of birth, name, etc.