Paid Up Account Still Owing!

I have recently settled my African Bank account with AFCard Consulting Services. CLIENT NAME: African Bank /MATTER NUMBER: ********** 002. I paid an amount of R 7,516.00 and received a paid up letter from them. I was SHOCKED to receive a statement from African Bank claiming that I owe them a balance of around R 12 000.00! I then visited one of their branches which confirmed this, I informed that I have paid this account but apparently the head office did not receive the notice from the 3rd party service provider. I NEED THIS SORTED OUT ASAP!!! This is really unfair.