debit order error

I called Cell C to change my banking details on 29/07/15. The agent I spoke to informed me they will start debiting in August from my new bank account since it was less than 5 day to the debit order date, I was happy with that since I had also called in to change my debit order date. On 05/08/15, I receive an SMS that my cellphone account is in arrears, I'm also liable for R70 unsuccessful fee. My new cheque account has a R115 unsuccessful fee. I've called multiple times and I'm still waiting for feedback. Why must I pay R70 whereas I was advised that the Debit order will run from August, who will pay the R115 unsuccessful. What about my credit record? I'm now a defaulter but I was honest and gave them my correct banking details