Netcare over-charged me and now taking forever to refund me: no honestly in dealing with their customer

I was over charged for an ambulance for transferring my mother from one hopsital to another. Nercare did not even bother to inform me about the over payment I made. I only discovered that I was over charged when I requested the invoice. I was then made to completed multiple forms as if it was my fault that they over charged me. I then submitted the documents to Desiree Liebenberg on 30 July 2019. More than two weeks later I have not had any feedback. I would like my refund and advise everyone to demand an invoice when dealing with netcare, otherwise you will be over charged and will never ever know about it. Very disappointed that such an organisation is not open and honest when dealing with their customers