Dreadwitch
Everyone sells your data... Have you used your number on here to verify anything? If so then they sold it, so for any other forum, social media or website.
I don't even trust banks or other official businesses not to sell data. I got a brand new phone with a new number, I'd had the phone 2 days and only given the new number to my family yet the spam calls and texts started.
The spammers don't even need to know who you are or anyone to sell data to them. They ring through an automatic dialling device which works its way through a list of phone numbers, such as the phone book. While the scammer is talking to you, his phone is starting to ring the next number on the list, or it just changes one digit of the last it rang. It could go from 000 000 0000 to 999 999 9999 if it had to. If no-one answers it just moves on to the next.
If you are paying attention to how they greet you, you will notice that the caller hardly ever knows your name, and their first words are usually something like "This is your bank." - Not the name of the specific bank, just "your" or "the" bank.