ABSA trying to exploit a deceased estate

We reported my mom's late estate on 20 April 2015, after her passing on 03 April to ABSA because that is where she had her cheque account, HL, CC and student loan for my brother. Debit orders went through and there was no salary so her cheque account was in arrears with R2146,27 to which ABSA sent a certificate of balance. Now all of a student the balance is R4312,87 why? We have settled all her other debts including the PL and Student loan debt. now we are querying this amount because we instructed Loraine Radebe to close the account and no one has answers. Absa claims it can give us a discount on the R4312,87, there shouldn't be a need for a discount because this account should not have been incurring interests in the first place as it was reported as a deceased estate. After my late mom banked with Absa her whole life now they want to exploit her in her death. Even with a 9.5% annual interest on the account, the balance should not be double what the original was at this stage. I really feel aggrieved by what Absa is trying to do to us, exploit the situation by quoting some arbitrary policy we have never heard of and to this day no one has even bothered to show the policy