Bad service by MTN South Africa

I app**** for a ZTE modem contract on 27 September 2023 and was told to make a payment of R282.20 before the contract could be concluded. I asked the agent if the R282.30 included the first month's data, and was told yes! I paid the R282. 20 at the end of September 2023 and the contract was approved. Now on 5 October 2023 nearly a week later there is a debit order against my bank account for R232.39. Why did this happen? It was not explained to me like that! Your calls are recorded! Please sort this out!