DISGUSTED Quotation and submission completely different

I needed to get al 4 my wisdom teeth removed, I got the codes from the Maxillofacial on 27 Feb 2025, I send it through to Discovery immediately for a quotation, Discovery then send me a quotation back on 28 Feb 2025 that everything will be paid, I then called to change the date from 14 March 2025 to 10 March and asked them will quote change and they said no as the Maxillofacial stays the same, I phoned again twice before the 10th and they said the quote stays the same, after I went to surgery and they send the invoice through to discovery now I need to pay R3500, I phoned them and they just saying it's being looked into, it's been 2 weeks now and still no reference received, feedback for their mistake and where I won't pay and my quotation stated paid in full, I am DISGUSTED in you as such a big medical scheme company! I am also not explaining to the Maxillofacial why I won't pay them, Discovery need to explain and make sure they get paid, as they also received the quotation that discovery will pay them in full.