Hand phone"이 아니라 "cell phone"입니다. 이건 단순 취향이 아니라 영어권 커뮤니케이션의 기본입니다.

The core point about 'hand phone' being unrecognised by native speakers is entirely correct, and the business-context argument is well made. But I would add that the same reasoning applies to _use_ as well as _recognition_ — a Korean speaker who writes 'hand phone' in an email signals that they are unaware of standard register, and the reader will not stop to check whether the intended meaning is 'mobile phone'. The nuance is not decorative; it is the message itself.