"When working for a previous employer, I left a phone message for a client. After hanging up, I spoke to my coworker about the work that we were performing for another client. About halfway through the conversation, I realized that the phone had not hung up correctly, which meant part of my confidential conversation was likely on a client's voicemail. I called and emailed the client asking that they please delete the message immediately, as it contained confidential information. The client verified that the message had been deleted shortly after. I now always make sure to hang up the phone properly after using it."