Priceline.com Quote me one price and add $800 charge to my card unknown online

 I booked atrip to Brazil andwas charged as quoted. I made a change to the return flight and was told the change would cost me $300 per ticket, with an additional cost of $30 per ticket for priceline to make the change. For two tickets, the total the change would cost was $660. My card was charged $733 per ticket, for a total of $1466. When I called Priceline and they said the person "documented the file properly" (basically told me it would cost $1466 and I agreed). When I explained what I agreed to, they told me "sorry, he said he told you and you have no options."