keep (going) on at (one)
To persist in reprimanding or criticizing one. If you keep going on at the investors, they're apt to get angry and leave.
keep (going) on at someone or something
to continue to complain about or scold someone or a group. Don't keep going on at him. Give him the dickens and be done with it. Please don't keep on at the committee. They did the best they could.