Mulbarton hospital *******

On the 30th of January 2018 when in for surgery in June of 2018 6 months later received an account for mulbarton hospital stating that I owned them 11500 rand when enquiried the amount I was told that the account is long overdue I requested a detailed statement as to the amount and why it took 6 months to be notified after speaking to so many people and not one could tell what the bill is for just final demands sms and emails but no explanation please help