No-one ever hangs up politely in films. Wives hang up on husbands, lawyers on their clients; the rugged ex-cop smiles with a twinkly eye as he hangs up wordless on his newlywed daughter. By its end the conversation has been squeezed for whatever it is good for, and goodbyes are the rind and pulp. Hellos, on the other hand, are everywhere, as the advert for the new iPhone shows:

http://www.apple.com/iphone/hello/