Bad service

I had a current account with you guys which I closed moving to another bank, I currently have a personal loan that I am paying for, did my best to alert you guys where to make your deductions which in April did not happen even though I got an email saying my banking details have been changed successfully! Throughout this current month I kept in touch with your agents on the fnb app verifying and confirming that you will be making a deduction at the right time this month all was confirmed! Days later still no debit, again I made contact on the app I was assured that it will be done which still did not happen! I find this act very reckless as well as unprofessional, can you fix this? Because if it carries on I'm afraid I might assumed you are trying to sabotage my credit score and I take thag very personal