Discrepancy between billing and benefits provisioning

Bad service. I took out a contract from MTN via their electronic channel. The contract comes with a router and 150GB data monthly at a monthly cost of R399. The package was delivered on 07 August 2020 and activated on 12 August 2020 and 34GB was allocated. My first bill is R456.00 and debited, so I called customer care a couple of times to query this also sent an email to customer care on 24 August 2020 ref no. ***8. I still haven't received any response from MTN about my email with the ref no. above. I was told that I was provisioned on a pro rata basis. There was no feedback, my issue is that I was not billed on a pro rata basis. There is a dicrepancy between the provision and billing. On the MTN's website they specifically state that there are no activation fees when you take a contract online. This means that I was only supposed to be billed the monthly cost without any additional charges for the first bill at a pro rata rate. I am aggrieved by how MTN is handling my billing and cancelation is a consideration since I feel that they are in breach of the contract.