I know what you mean. I am so careful on what I put my phone number, e-mail address, etc. It seems you get flooded with all kinds of stuff on your computer/phone. Nothing is truly free out there.
When we moved 5 years ago, I thought, as we were getting a brand new phone number, we might have some peace from unwanted calls, scammers, etc. No dice - we were flooded with junk within the week. So the phone company must also sell that info. When someone asks for my e-mail or phone number I don't give it out unless absolutely necessary as for Dr. or clinic info.