Incorrect debit date

Contacted Telkom to change my billing date to the 20th in begging of Feb as i could not wait for them to debit on the 31st consultant confirmed that it has been initiated to my horror they have now started 16th of month instead of the 20th as requested and as a result they putting my account on a minus they have done for March called in today spoke to a defensive agent Asaad Fredriks who could not give me a straight answer why that was done claims collections can debit anytime of the month advised him he must send me a clause that states that nothing has been sent till now i spoke to him 11:30 am 2021-03-17 now i am being charged by telkom fees because they didn't initiate the correct request and as for Asaad he seems clue less and doesn't give correct answers and customer service can someone contact me on via email .