probably a medical debt collector. I've been getting hangup phone calls like this for a couple of years, ever since I complained about multiple billing and alteration of electronic medical records. i no longer answer these weird calls, but when I did,k the callers insisted they did not have to obey federal and state laws so long as they did not give their real names and gave a medical-related name instead. I started getting them from this area code, where my dad lives, when his doctor insisted on getting all my cellphone numbers for use in case of an emergency concerning him. i told them not to call and showed the cellphones (calling which is illegal without the owner's consent), but I wouldn't put it past them to call anyway. they left a message on my dad's landline that clearly was illegal--but HHS's Office of Civil Rights has made a policy decision not to enforce the laws concerning alleged medical debt collection. So they're the biggest part of FTC donotcall list complaints, but the FTC agreed with the OCR to let them handle these, and OCR has decided nonenfocement is "enforcement with heart" for doctors and insurance companies, but not citizens, patients, etc.