Crazy billing

I would like to understand the way ER24 are running their things. On april 2017 i was assisted from badplaas resort to Barberton hospital on their ambulance. And from then on no statement was sent to me for billing, suddenly they are calling saying if i don't settle the amount of R10 800.00 , they will blacklist me because they have been calling me without a success. I just want to understand what that high amount is for because they didn't even offer me any medication. Since I have to settle the amount myself although i didn't get any statement from them, i find it very unreasonable. How do they get to such an amount ?