I will not pay unless I know what this is for - BAD SERVICE

i have been receiving notifications from Elizabeth Mbongwe for several months now regarding an 'outstanding amount' that needs to be paid. Each time the mail comes in i'v'e asked Elizabeth to send through the breakdown of this so i can understand what this is as i was under the impression my medical aid covered the bills submitted. NO RESPONSE and my mails are deleted without being read. I've tried the contact number provided and no answer. this letter advises i must make payment by the 9/11/17 to avoid legal action - I am not just going to fork out an amount and NOT KNOW WHAT IT IS FOR. Can Elizabeth Mbongwe kindly contact me