Account reaches attorneys but no account was sent

In July 2015 I had taken my parents for routine blood tests which are covered from their chronic benefit, of course I go through the usual of filling in the forms for payment and contact details etc. a few weeks later I receive a bill stating there are no medical savings to pay for the pathology tests done, I then explain it was for chronic and they are covered for the management for certain conditions, the consultant politely says the claim will be re submitted, after that I do not hear from anyone I assume the bill was taken care of. In February 2016 I get a call from attorneys demanding outstanding balances, bear in mind in the interim I have not received a statement or invoice or any bill whatsoever stating that there is an outstanding balance or query with a portion of the claim. Why should I be responsible to pay for a claim which had to be claimed from my medical aid chronic illness benefit? Furthermore no attempt was made to contact me during this time for either payment or re-submission of claims, how does this become a legal matter when the accounts department of lancet made no attempt to contact me? I need answers A.S.A.P