Frustrated and helpless customer

I went to ghandi Square branch to change payment date in February. The agent said he changed the date. I have an existing contract, I took an additional contract, he to told me that all will be combined n be deducted in April. The the amount will R700. In April R1100 was deducted, and thereafter I received invoice of 1900. I called call centre, they said I'm being handed over to debt collectors. I explained myself, and asked to escalate my query. They said I must go back to branch. What a poor service. Imagine I was working from home, staying in Pretoria, I must go back to ghandi Square. Imagine if I took that contract in Durban, that means I must catch a flight to Durban. I went to ghandi Square branch, met with the manager, the agent saw his fault. Both lodged a query, and the manager said if not resolved, the agent will be accountable for that, he agreed. I received case number, after 4 days I called, and they told me that the case has been closed without being notified. I called that agent, he said they refused to reverse the rejection fee, he said he will reimburse me. I worked hard for my credit score to be where it is now. Debit went through n bounced. Why must I be penalized for your mistakes. I sent my query to 2 managers and the complaints dept, no acknowledgement nor nothing, always I'm receiving messages that my service has been interrupted and since then I'm having trouble with connection. Today the 26th, I received messages that my account will be debited again on the wrong date inclusive of the rejection fee.