The voicemail of the client, this was a very important deal for the company and at that point I was under sheer pressure from my boss to get hold of this customer. I had attempted for, I think, two weeks to reach him and he was not calling me back and I finally got hold of him and I said to him, because we had quite a relationship, well-established, "I'm a bit disappointed, given the urgency of the matter, that you hadn't called me back" and he said to me, "But I called you back and I left a message on your voicemail" and I said, "No you didn't, did you?" and he said, "Have you checked your voicemail?" and there was a bit of a heated argument -- not argument but a bit of a heated discussion and I said "Okay, I'll look through it", we went through the conversation; he said, "I left you the message and it was okay, don't you worry about, we will do it", I said "Okay, that's fine".
I hung up and I checked my voicemail. I had a bad habit, with hindsight, that was to keep my voicemails packing up into my voicemail box, which we know afterwards was a bad suggestion.