Final Demand issued without ever issuing account

I gave birth to my son at the Park Lane on 12/05/15.On the 23/09/15 I received a letter of Final Demand in the post threatening me with Legal Action if I do not pay.This is the first communication I have received from Netcare that there was an outstanding amout- I thought it had been covered by discovery.I promply emailed the contact person on the letter but have had NO response. Netcare was quite happy to send an extremely rude,threatening letter of Demand without trying to call/email/ post me an actual account & was happy to threaten me with legal action & ubmitting my details to the credit burea if I do not pay- but has failed to make ANY contact with me even after receiving my email. This kind of customer abuse is totally unacceptable & as a medical doctor myself I will in future think twice before using netcare doctors & facilities to refer my patients to. Surely I am entitled to see what I owe money for so that I can bring it up with my medical aid prior to receiving the totally rude &uncalled for letter of demand. If netcare had my NEW postal address to send this letter they must have had all my details & could have found some way of communicating with me that money was owed