You may be able to take one or two of the prerequisite courses online such as psychology and anatomy, but you must attend most classes in person as you must practice the techniques that you are learning. A great deal of the learning is done “in the field” – on ambulances and in the ER. Some programs of study cannot be learned via the internet. Would you want to go to a doctor who earned his degree online (which would be impossible) – I think not.
Minyan Gal is correct. There are hours and hours of hands-on practicum work that goes into becoming an EMT. if there IS a company trying to reproduce that with on-line studies, I would stay far, far away!