debited on incorrect date

My debit order is supposed to run on the 20th of every month which has been happening for over 3 years now. However for September I was debited on the 25th, I called your contact centre now and was told that they don't know why this happened. Due to you debiting me on the incorrect date my debit order has returned, and I have a dishonouring fee on my account of R90. Reimburse me for the R90, due to your negligence, and issue me with a letter confirming that due to your error I have a return debit order on my account as this has now affected my credit score!. Do a double debit for my subscription in October.