SIL#1 is getting those kind of calls from a medical billing company. They want him to give them $800. They say that because of HIPAA privacy rules, they cannot tell him who the doctor was, what was done, where it was done, or when it was done. The ONLY information they will give him is that somebody with HisFirstName HisLastName owes somebody money for doing something medically.
He has had minor surgery in the recent past, but believes that he covered all of the copay bills that he was supposed to pay; his insurance was paying the lion's share of it.
So they're confident enough that this bill belongs to this specific HisFirstName HisLastName that they expect him to pay $800, but not so confident that they can tell him anything at all about his own (supposedly) medical treatment. Because of HIPAA. OK...

If HIPAA forbids giving a patient information about that patient's own medical treatment, then doctor's appointments must get really confusing.

Patient: "So should I be worried about this mole?"
Doctor: "I can't talk to you about any moles you may or may not have. That would be a violation of HIPAA."
Patient: "But it's
my mole. The whole reason I made an appointment was to figure out if it's benign or not."
Doctor: "I can't discuss the reasons for my patients' appointments! HIPAA!"
Patient: "But, Doctor, I just want to know if this mole is dangerous. Does it need to be treated?"
Doctor: "I can't talk to you about that! HIPAA!!"
Patient: "Did you even look at it? Why did I bother coming?"
Doctor: "I can't talk to you about anything I might or not have looked at, or why you came to my office! That's what I've been telling you! Your medical privacy must be protected!! HIPAA!!! HIPAA!!!! HIPAA!!!!!"
Patient: "...Either you're going insane or I am."
Doctor: "Who told you that?!?"