When Ezekial comes to the radio he can hear background noise and people talking from the other end. All the radios used on the show are PTT so unless someone is there to push the transmit key nothing it sent. They even added a line-crack noise when the other end cuts transmission before Ezekial sits down to confirm this.
Aaron has now seen Gamma deliberately poisoning their water supply with walker guts twice yet he still hasn't reported it even after people start getting sick.