Lancet Lab don't want to revise bill from Medical Aid rates to Cash rates.

My daughter was taken to Chatsmed trauma unit & needed some blood test to be done & we clearly instructed the staff that our Medical Aid (Medi help) only deal with Ampath Lab but without our authorization Lancet Lab was called in to do the bloods. No forms were signed by me the principal member. Lancet Lab had all the medical aid information & went ahead with the test & then billed the medical aid. Medi help rejected the claim & now left to me to settle the bill. I do believe that I should always pay for services rendered but I did not ask Lancet Lab for their services, but I am willing to pay but not as those ridiculous medical aid rates. We all know that the cash rate is much lower than medical aid rates & I did call Lancet Lab to ask for a cash rate to do payment but was told that the bill cannot be amended so I refused to pay the bill. Fast forward to the 15 March 2024 I am now handed over to a collection agency SCS (PTY) LTD who has no history about the case but demands payment & after my explanation to them, they didn't bother to refer to Lancet Lab but just listed me as a default client. If Lancet Lab can't revise the bill, then I can't see a way forward.