They can also get it through autopay records. Banks give that out to them when they SHOULD NOT. Why do Banks give that out to them? For debt collection legalities. Without it they cannot legally collect a debt.
And this is why it is absolutely stupid to use autopay of any kind...
I’ve always either received a paper bill or used a credit card. I refuse to give an SSN to dr offices or utilities. Only financial institutions are legally required to have it.