"ne" or "na" before verb without "ka"?

Example: ana kant3llam “nektb”. or ana kant3llam “naktb”.

why do some people write with an “e” and others with an “a”?
what’s correst?
what about the pronounciation?
do i have to pronounce the “a” like the french “è” (ouvert)?

    naktb= /nèktb/

If you ask me, that’s just a matter of accents! I write as as: nktb! But yes, it sounds close to the French è.
It doesn’t matter how you write it, as long as you got the conjugation right. See, this is just transcription, and you’ll find a lot of differences in the way people write Darija in Latin letters.
I hope this answers your question.