Some foreigners complain that English loanwords in Korean do not have the same meaning in English. Korean is not the only language where loanwords evolve, they do in all languages. Promiscuity means what it means in English, but the word was borrowed from French where it means "proximity".
Therefore Koreans have the right to use whatever word they want to use what they want to describe in their language. If they want to call their cell phone a "hand phone", foreigners have no right to tell them to start using "cell phone" or to use the Korean term hyudae chonhwa, as much as the French have no right to tell Americans to mean "proximity" when they say "promiscuity".
Without being too political, "hand phone" is not Konglish when it is used in a Korean sentence, nor is it "code-switching". It is a term that is now a full member of the Korean language, and Koreans treat it as one.
What is Konglish then? Konglish is a "sublanguage", a language spoken by many as a second language but by few or no people as a first language. It is a language with grammar rules, words and everything else languages have, but those rules differ from any other type of language and the language is therefore called Konglish.
Since Koreans interact relatively little with native English speakers, the arising of this sublanguage was inevitable. The language is a mixture of English and Korean patterns. It may sound cute to some foreigners, or be a sign of ignorance to others, it will nontheless be very difficult to teach Koreans not speak Konglish and to speak American English or whatever English instead.
When speaking a foreign language, foreigners calque their native language. This means that they will use the conversation etiquette I described in previous posts, and ask the same kinds of questions that they ask foreigners, use the same appellations, titles, respect forms etc.
Since it is inconceivable for Koreans to call a teacher by his first name, they will call him "teacher" regardless of the language they speak. Therefore if you are an English teacher in Korea, most students will call you "teacher". They will also use Korean expressions in their cultural context, so when they ask you about your kibun they will ask you "how is your feeling".
English loanwords which experienced semantic change in Korean will be used when speaking Konglish. For example, words like "announcer" (anchor), "one piece" (dress) or "live English" (colloquial English) will be used by Korean English speakers.
Other rules include drooping the final -s plural marker when it is phonetically a [z] sound("two car" instead of "two cars", but "two cats" and not "two cat") dropping the auxiliary "to be" ("no one there" instead of "no one was there" or "if you wanna pretty" instead of "if you wanna be pretty" etc.) and many many other rules.
Asking Koreans to switch from Konglish to American English would be like asking Americans to switch from American to British English. Remember, Korean people's intention is not to make lots of American friends or to be more Americanized, but to get a decent TOEFL score and get a decent job.