Unfair treatment

I recently received a call from fnb collection regarding my personal loan I have with them . I was informed that my account was in ereas , which I disputed the information as she was inisting that my payment date is on the 15th which to me it was the 1st after a long arguement I then advised her to refer to my contract and she did it came out that the mistake was on FNB side as they loaded the date incorrectly during capturing .

The lady then proceded to inform me my account was still in ereas on the system nothing has changed I still need to make a payment . I requested to speak to her superior since we were not reaching any solution.

She then refered me to Patrick who is ateam leader .I told Patrick to rectify the mistake. A Day later I received a call from Patrick informing me that in order for fnb to fix their mistake my instalment Will increase to R1700+ from R1600+ I asked him if he is aware that my initial installment is R1500+

when i asked why is my instalment going up from 1500+ to 1700+ then Patrick told me my last installment will be less but he can't give me the exact amount I then informed him I don't have a problem with that provided I get a written confirmation to all that he was telling me. today I woke up to an sms saying I'm owing and they couldn't find funds in my account

Please rectify my credit score and give me a way forward regarding this matter urgently.

My email ********** ********** 714