caller ID actually showed 115619104713. Robocall which we receive frequently, "Hi this is Rachel from Cardholder Services..." says it's urgent... offers rate reduction or something.
Do not bother trying to talk to a person or pressing the number to remove yourself from the list because it won't work. Well, maybe try once so you can tell FCC you tried.
Keep a log with dates and times, try to capture the number (either with caller ID if you have it, or use your telephone company's star code to get the last incoming call, usually *69), and file a report with FCC.