On a London to Plymouth train journey, I once encountered a particularly obnoxious "very important businessman" type who insisted on holding an interminably lengthy and very loud call to brief some hapless subordinate. As he bellowed into his phone (in the quiet carriage, no less), I got so fed up that I tapped him on the shoulder and asked if he wouldn't mind speaking up a little as I couldn't hear properly and wanted to take notes. He shut up after that.