If memory serves though, there is a surcharge for phoning for a taxi. Is that correct?
Is there also a surcharge for ordering one through FB?
Maybe so, not sure. I don't ask prices as I own a car so I don't taxi much other than to the ferry and back.
I'd reckon most tourists would find an extra 5-10 peso convenience fee acceptable if that means they can call a taxi that picks them up on location, have the taxi number written down (think lost phone, safety, etc), and don't have to price haggle.