A qualified ESL teacher should be able to teach everything - from speaking and listening to reading and writing including the sub-skills of pronunciation, grammar and vocabulary. Oral English classes including conversation require proper preparation, you just can't walk in and start talking. For conversation courses, you need to write good lesson plans as well.

On this site, I have published a lesson plan template that is very comprehensive and that follows a certain didactic model that I have been using and also recommended to ESL teacher training students over the years. I can mail the link to this lesson plan template to anyone who requests it.

A qualified by-way-of-birth oral English teacher will be hired to teach oral English because that is what the employer wants. They might have a-you just down the corridor to do the English Lit and for the writing skills. And they might well pay you much more. I think that's fair enough.