Account for wisdom teeth

In January this year my son had remove his wisdom teeth. I submitted a quotation to Denis. They gave me an authorisation letter in which it was specified that we had to make a co-payment of R1700. A month ago I received an account from the dr that operated and they said that I still owe them R3187.15 which my medical aid will not pay. The medical aid only then told me that there was a paragraph on the authorisation that reads \...Treatment will be covered at the scheme tariff