Other mistake: In the scene where Bateman is about to murder Paul Allen, he turns on the CD player and walks towards the axe meaning to say "...song's so catchy;" but if you watch his mouth, you can see that in place of the word "catchy" there is a blatant voiceover. Who knows what he said in the original shooting. (00:28:25)
Other mistake: Several close-ups of the business cards of Patrick Bateman and his associates reveal a misspelling of the word "Acquisitions" (the "c" is missing - not a small error, given that this is the name of their department).
Answer: There are two possible answers. First, Carnes doesn't recognize Christian Bale as Bateman, instead thinking he is someone named Davis. He insults Bateman and thinks "Davis" left the message as a joke. Realize also that someone claims to have seen Owen/Allen in London, but mistook Herbert Ainsworth for him. Second, Bateman is delusional and only thinks he killed Owen/Allen, who is in fact alive and in London.
Greg Dwyer