Telkom Billing ERROR

Why is Telkom debiting my account on the 15th of the month when my contract that I signed/agreed to with Telkom states that my debit dates would be on the 25th of each month? As a client/consumer of Telkom products were you not supposed to get instruction from me to go debit my account on a different date from that which is stipulated in the contract that I have with you?

Also why is telkom debiting my account with amounts that are not specified on my invoice.

Why should I wait 48 hours for them to investigate and I cannot reverse the debit order.

sent all the requested documents,and not a single consultant has contacted me.

Telkom my account is not in arrears and you have no right to debit my account with an amount that i do not know.I have sent several emails to Telkom. Thank you