+442088971059 & +442088976930, Payphone, Ground Floor Baggage Hall, International Arrivals, Terminal 1, Heathrow Airport, Hounslow, London

Real neat addition here. You'll get an interesting answer to this. It could be anyone from anywhere in the world. The payphones are positioned right next to the baggage reclaim belt. It is the very first of 5 when you come from the plane.