Wesbank affecting my credit score

I fail to understand why should I be held liable for a mistake that was made by Wesbank. The reinstatement was only finalized on the 10th of September 2018, which was yesterday, on which the installment for September had already been paid on the 24th of August whilst the account was still under debt review installment. So my understand and it is sensible, that if you make changes later than when the installment was due, which is the 1st, the readjusted or changes can only take effect with the next installment. So why am I in arrears of R5000 +/-??? I just checked my credit profile and realised that a new account has been opened under Wesbank with a new account number. Would you please change the status of the old Account: ********** 3873 to "Closed" because it is affecting my credit score which went down by 30 points because my account count has gone up by one and the old account is still open which I do not understand why a new account was opened instead of reinstating the initial installment.