In The Holiday (2006), Iris had a phone conversation with 2 persons at a time: Graham and Amanda Woods.
Iris: I can't believe that you have had sex with the woman staying in my house.
Amanda: He told you that? Oh, my God! Oh, my God! Oh, my God!
Iris: I thought I was talking to Graham! Could you just hold, please?
So how did Iris correctly guess that Graham had sex with Amanda Woods?