Who called from 5712237869

Has called three days in a row but no one speaks when I answer.

Has called several days in a row and leaves no message when I or the answering machine answer.

Has been pestering us for a couple of weeks now, usually several days in a row. Never leaves a message, never responds to answered calls.

Has called here several times a day for quite a while. No one is ever there and they never leave a message. I'm a little tired of it. I need to find some way to get back at them.