They keep calling and asking about some one I have never heard of, Its a robo call about a business matter

I have been receiving repeated phone calls to my office phone, before or after hours, for a woman named Rebecca to call a toll-free number.  I finally called the number after weeks of harassment.  The automated answer requested I call one of two numbers, one was for DirectTV, the other for ADT Home Security.  I called the DirectTV number, and after a series of automated menus, got a real person who said no one by that name or phone number was on the account.  I then called the other number, which led me to a message that said to call the same number I had just dialed!!  I then looked up ADT security online and called their toll-free number, and was once again led through a series of automated menus, and then was AGAIN told there was no one by that name or number with an account!!  This is so frustrating!