Also keep in mind that whenever something is "free" your data is what pays for it so it's worth being suspicious. I would be willing to bet this is how you have got onto the spam list, quite often it will be a competition where you enter to win something but what they're really doing is collecting marketing information to sell to data brokers and they just bet on the fact that most people don't read the terms and conditions.
Here is a link that might help, in that most responsible advertisers will consult this list before trying to contact you so if you add your name it might cut down how much marketing you are getting.
https://marketing.org.nz/consumer/do-not-call
Also here's a small trick you can use when signing up to new services that will allow you to see if a company has sold your data provided you're using a gmail address, so as an example say you are signing up for an account with Facebook and it asks you for an email address, you would type yournormalemailhere+Facebook@gmail.com you just add the +"example" before the @gmail.com it can be whatever you like. You will still receive emails to your normal address but the recipient part of the email will reflect the ones you give out when you sign up to each service.
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