First of all, it is "KONnichi". And lastly, a lot of people write in roman characters the exact way it would be written in Japanese kana. While the SOUND of "subject marker" is WA, it is in fact always written as HA when using kana. The same is with the particle that sounds like O, but it is always written as WO when using kana. and E versus HE in kana.

Hello! First, saying hello in Japanese is Konnichiha, not Kunichiha. The syllable is "ko-n-ni-chi-ha". Maybe to pronounce this word is difficult for English native speaker. As you say, we use "Konnichiha(こんにちは)" for writing, but pronounce "Konnichiwa(こんにちわ)". To pronounce "konnichiha" is wrong. Even though Japanese children write "Konnichiwa" incorrectly sometimes (not everyone). And, do you know some Japanese grammar? Konnichiha has a root from "今日はご機嫌いかが？Konnichi ha gokigenn ikaga?"(How are you today?). The long sentence had been omitted to "今日は(こんにちは)Konnichiha". So, Konnichiha's "ha" is same as "ha" Indicates the topic of a sentence. Incidentally 今日(こんにち,Konnichi) can be translated into "today". And, "こんばんはkonbanha(good evening)" is same as Konnichiha. We write "こんばんはkonbanha" although, we pronounce "こんばんわkonbanwa". And, こんばん(今晩) means "tonight". This might be difficult, you can ask me if you want. Thank you.