This is totally correct. HSBC will ignore your demands to stop calling, and will never leave a message on the machine. I have seen several numbers, most often 800-684-8429. I went online and took my home and work phone numbers off of the account and put on my side business phone number, which is on a machine all day and does not ring audibly. i did this today; we'll see if this stops the harassment. I get calls even after a payment is made; they start on the due date, even if the payment is made online and I can see it on the screen.
I have also read that FDIC collection practices specifically prohibit this kind of harassment. I don't know if there are liquidated damages available under that law / regulation, but if there are, there has to be an attorney somewhere who's willing to file a class action lawsuit!!