Zwei am Zug (1970)

Sandra, a pub landlady, meets Otis, a travel agent. The two initially clash as they learn more about each other from overheard phone calls than they would like. But they get talking, discover an amazing affinity and find each other to be valuable love advisors for their personal relationship problems. When Sandra's husband Christian meets Otis' best friend Bill by chance one day, the emotional chaos is perfect.