I have never been an EFL teacher, but I did research the possibility, and the reputable schools will not accept an online TEFL course as a qualification. There's a good reason for that: the only way to learn how to teach is in an actual classroom with a mentor. If a course doesn't include practice teaching, it's just a piece of paper.
I used to be a university-level foreign language instructor, and no online simulation can duplicate the experience of standing in front of live students and making sure that they stay engaged and actually learn something.