Too much billing

Mine is on billing. I am here to complain about the payment. In April I was offered a GREAT deal and I grabbed it. End of the month, a debicheck of R400 was sent on my phone and I rejected. I asked the call centre agents what that meant and they told me it is just an estimate of how much maximum I am given by my bank like a maximum amount. I rejected that debicheck. Then another one for R85 came through and I accepted it. It was deducted from my account. Now, on the 1st of May, MTNSP deducted R395.03. Now, the chatBot that I have to use to get a query logged in not giving me options to explain all this. MTN customer service us not clear as well on all these amounts. How did we get to R85 and R395.03 being deducted from my bank account yet I agreed to a R270 data deal? Can someone please explain to me and correct what needs to be corrected or make me understand why I paid more than R400.