Early collection of credit card APO payment/debit order

My debit order for my FNB credit card has always been collected round about the 6th of each month since inception many years ago. This month, FNB decided to collect it on the 25th of the month, yet my statement still reflects that it will be collected on the 6th of December 2017. I enquired about it from the card division and they told me that they sent to SMSs stating the following "Your credit card Auto payment date will be on the 25th. Reply NO to opt out or call the no on the back of your card." This was on the 9th November 2017, prior to my credit card statement run dated 13th November 2017. Please explain how this constitutes 30 days notice as per the initial credit card contract signed. Furthermore, if you are going to change the payment date and do the collection earlier, then you need to make the statement run date earlier in order. If this is the case then I will never benefit from the 55 interest free credit. This is false advertising and *******. If this happens again, then I will report you to the Ombudsman and also close all my accounts with FNB. Why must i as a client be prejudiced and have to incur telephone costs to cancel/update an auto payment request initiated by FNB. This was not my mandate with FNB as detailed in the Credit card terms and conditions and I do not accept this new auto payment date.