In January, I booked a private ambulance for $500, to transport my daughter from Whittier Emergency Medical Center (not the PIH Hospital) to USC. WEMC (who had given me the name and number of the original ambulance), then canceled my ambulance, because they said that using AMR would mean that it would be covered by my insurance. AMR charged $1,634 for the $500 journey! They have already received $987.20 from my insurance and are now relentlessly pursuing me for the other $646.80.
Make sure you understand how much they are going to attempt to inflate the charges, before you agree to use them!