This may not be the best question for this community, but I believe it should be open ended.
The reason I have been thinking about this question is because someone once said: "as soon as you turn 18, card companies will start sending you offers and advertisements". How do they get that information? Is it through my bank or something else I naively signed up for?
I am a big "opsec" nut. I take steps to not give out my information. I do not give information to social media websites as I do not even have an account on most of them. I only just closed my only bank account I ever had. I do not have any subscriptions or services. And you can assume the rest.
I think this would be a good test to see what may have leaked to companies so far.
I don't know many other ways I can ask the question. I just want to be prepared and be unknown.
Not exactly asking for advice, just what precautions everyone else has taken in their life. If I am asking in the wrong place, I hope I can get good redirection.
Voter registration is public information and sufficient for cold callers.
If you live independently you will inevitably have to make privacy sacrifices for the sake of expediency. Having a bank account is probably going to be one of them. There are many essential services that you use but probably do not think of as an eighteen year old that may share information when you provide for yourself such as your phone carrier, ISP, utilities such as power, water, gas etc, insurance, health services, education or certification providers, employment or recruitment agencies, the list just goes on and you will have to thoroughly evaluate every company you interact with and in many cases there will simply be no realistic privacy respecting option.
Keep fighting to protect your privacy but don't put an impossible burden on yourself to be perfect. You will make mistakes, you will make compromises, you will probably get spam. Welcome to late stage capitalism.