Being handed over for a invoice that has been paid in FULL from my Medical aid

worse finance department- Son went in for an emergency, they put the claim in with the incorrect codes so medical aid rejected, only for me to received a SMS that i will be handed over if this account isn't paid, I contacted them to ask what was outstanding as i haven't received any invoice or communicated before this-Even though before my son was seen to with a head injury-i had to open a file again so they had all my details. I then sorted it out with my medical aid and was paid in full from them, i called the call center top give my medical aids reference number for the payment and i WAS HANDED OVER EVEN THOUGH THE ACCOUNT WAS PAID IN FULL! This wasn't my error by your error!!!! had endless phone calls which has all been unsuccessful