Mr Price Account Double Charge for making payment a day later

So I opened an account online around 28 January 2019 and then received statement after making purchases of my instalment due for 28 Feb 2019 however last payment date being the 7th (which I was told by collections agent). I made full instalment payment on 8th of March '19 which was a day afted cut off and would understand that extra arrears would be charged on my account. Xolile gave me a call on 8 March around 17:19 to be exact informing me that my payment is due. I told her that payment was made that day and she confirmed,only to tell me I now have to pay another full instalment as the arrears charged for missing one instalment would be doubled. I fail to understand this and she demanded that I make a full instalment of R165 9/03/19 so that my account be up to date for the month of March. I was not informed about this when my application was approved (mind you I never received a welcome call from Mr Price to read out important disclosures to me in line with FAIS and TCF legislation). My 1st account with the group and already I have issues. I want this to be escalated and also want proof that I agreed and signed or voice-log that when u pay a day after the cut-off date, that you need to pay double. When I asked Xolile for details to Mr Price Complaints department, she told me that the call recording will be escalated to her team leader as there is no complaints division - so much for a licensed and registered credit provider?? ?