Telkom debiting me on wrong dates

On 17th of November 2019 I signed a contract with Telkom for a mobile device and requested to be debited on the 25th of each month. The past two months I have been debited on the 5th bearing in mind on the 14th of January I called in and requested to be debited on the 25th of each month. The consultant I spoke with assured me that the debit order has been changed from 5th to the 25th of each month effective from the 25th of February 2020. To my surprise I received debit order sms notification on the 8th of February from Telkom. I called customer care and the lady I spoke with told me that the initial debit date was changed before the contract was older than 3 months. I am annoyed and dissatisfied because: 1.) I requested to be debited on the 25th 2.)where did you get the information for be to be debited on the 5th. Contract I signed stipulated the 25th). 3)I was told on the 14th of Jan that it has been changed to the 25th effective in Feb. 4.) it’s such an inconvenience to sign up for something and someone or the system decides to debit me on the date where I don’t know where they got it from. Now I need an explanation and how you going to own up and remedy my situation. What does this mean about the cellphone contract I signed? Valid or void?����. Not in legal but can always seek advise.