You should write konnichiha (こんにちは, but the は is an particle that should be pronounced as "wa".....so you write "konnichiha" and read "konnichi wa".

First, the pronunciation is "konnichiwa". And, the correct writing is "こんにちは". Sometime, even japanese people write "こんにちわ", but it's not correct exactly. Basically "は" pronounce 'ha', but sometimes it will be 'wa'. "は" has 2 pronunciation.

It's written "konnichiha" but the は here is pronounced as わ In the past time わ is not used frequently As the は is an particle here,it should be "wa" It's kind of particular.