Incorrect billing

I was admitted at Ahmed kathrada lenmed in Lenasia on the 21st December 2022 for the delivery of my boy. Almost 11 months later I get emails from lenmed that my account is in arrears. I contacted my medical aid and I was informed that the hospital sent incorrect codes that led to the account not being paid. They later said the account has become stale according to their policy payment enquiries should be made within 4 months after hospitalization mind you the hospital only communicated to me almost 11 months later. How am I in debt for negligence caused by the hospital? I sent emails even to the same email address that has been sending me emails but they have suddenly gone mute. Should I find myself under debt review because of this negligence it won't end well. Hopefully they will see this because it escalates cause I'll do anything to protect my financial record. The fact that they don't even respond to emails is sickening to the core.