Khan not Kahn
It's Khan not Kahn!
Kahn is a surname used by people in Western society.
For example:
http://www.imdb.com/name/nm0001404/?ref_=fn_nm_nm_4
Khan is used as a name or title in some Asian societies.
Some people who used the name or title of Khan were very evil, way down there in the bottom dregs of humanity with Adolph Hitler and Stalin.
https://www.quora.com/Was-Genghis-Khan-more-or-less-evil-than-Hitler
https://www.hawaii.edu/powerkills/SOD.CHAP8.HTM
If my parents named me Khan I'd change it.
If my surname was Kahn and I caught someone confusing Khan and Kahn I might get angry enough to physically attack them for the insult.
Remember it's Khan Noonien Singh not Kahn Noonien Singh!