"Hey, did you just call me a liar?" "No, but I called you a crook." "Huh? What are you talking about!? I seriously can’t believe you."
You know that 詐欺 is "fraud." An expert at fraud (詐欺) is someone who does this a lot and possibly for a living. A swindler, some would say.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own. Will help to know the reading of 詐欺 as well.