I took an online course with ITTT about 8 years ago. It was a good program and completely online. At the time, they had a package deal, where I could pay for the TESOL course and they provided another course for free (either business english or english for young learners).
I took this course as well many years ago, and received interviews. It helps to have teaching experience already, if you are planning to take a fully on-line class as some university employers will not accept such a course without some teaching experience.