African Bank confusion with debt collectors

I am harrased by two collection companies (NuDebt Management and Coombe Inc), both for the same African Bank Account. Both claim that they were requested by the Bank to collect the money. I have been paying NuDebt for a while now, without any problems. Coombe Inc is sending me daily messages as reminders to pay, and adding charges to the account for each sms. I have sent them the retrenchment letter SEVERAL TIMES, informing that I do not have income this month to make payments, but with NO response regarding the matter. I have meen sending the sms's from Coombe Inc to NuDebt Management, and the email reminders from Nunebt Management, and to date they have not responded or made any effort to sort out the Confusion, and neither have African Bank for that matter. It is concerning that such confusion is left unattended to, but it is now referred to OBBSA and the Credit Regulator.