Continual phone calls after being asked to remove us from their call list

They are calling for Alan a former employee. We have told them multiple times that he no longer works here. We have asked to be removed mulitple times and they are not doing it.  When asked for a phone number that we could reach them at they hang up.
We have told them that they are calling business phone numbers and they still keep calling multiple times per day.
I want the calls to stop immediately.