Internet personal data & big business -how do they get my info?

I went to change my password on ebay. I have never given ebay my past two or 3 phone numbers, have never given facebook my exact address or phone number

ebay has my phone number (willing to send me a text to verify) although they have been asking for my phone number for over a year via their generic operating software (I notice they don't ask anymore)

I had to give my phone number out after i moved for establishing some bills and now ebay has my number?

people say don't share your personal information but what is the point? I had to give companies my number to establish utilities and now a company i did NOT want to have my info does?? WTF!?!

i need education on privacy because my 1990's training is clearly outdated

i would much rather be close to 'off the grid' than a commercial statistic for big business and gov

i shouldn't ***** though because the chinese have ALLLLLLLLLLL of my most personal info and life history and social security number because OPM which runs the gov clearance got sloppy and hacked -even life lock doesn't help outside the U.S.

this constantly pisses me off what can we do?

Here's just the tip of the iceberg if you really want to see one answer to your question.
Are you ready? This is all the data Facebook and Google have on you | Dylan Curran