OT but am reminded of another similar trick, if in the reverse situation ie someone on the phone, yadda yadda yadda, can't get them off, take the phone (only works for mobile or hands free phones) to the front door, ring your own door bell
"oh dear, I'll have to go, some-one ringing the front door bell" - which is true, someone is, and they can even hear it themselves down the line