YOU SAID:

I would never do that.

INTO JAPANESE

私はそれをしないでしょう。

BACK INTO ENGLISH

I won't do it.

INTO JAPANESE

私はそれを行うことはありません。

BACK INTO ENGLISH

Not that I do it.

INTO JAPANESE

私はそれを行うことはないです。

BACK INTO ENGLISH

Not that I do it.