YOU SAID:

never have i never not done that

INTO JAPANESE

決して私はそれを行っていません。

BACK INTO ENGLISH

I have never done it.

INTO JAPANESE

私はそれをやったことがないです。

BACK INTO ENGLISH

I have not done it.

INTO JAPANESE

私はそれをしていない。

BACK INTO ENGLISH

I have not done it.