Right
Computer generated numbers would work and I didn't think about that. Since my number is listed they always know our name.
Private numbers can also be obtained nefariously. Individually it is easy (about a $15-20 item) but I am not sure how difficult it would be to get them by the hundreds.
I am not certain that the phone company has any liability for the privacy of the numbers. Unless things have changed, any phone company employee can access private numbers and they have been known to have arrangements with individuals that need to know.