Bad service

I posted regarding Wesbank that I had an arrangement to pay my arrears for 9months and I did. My 9 months ended in 25July and usually few weeks before the 25th they were sending an sms as a reminder. 25August I didn’t receive any sms because the 9 months was finished. After the 25th started to receive missed calls from wesbank guess what they say my account is in arrears. How come now coz I’ve been paying on the 25. They send me the statement some of the months they updated I paid on the 26 which is wrong. Now they telling me I must pay extra for 4 months again. I asked the guy to please explain to me how is that possible he hasn’t got back to me and it’s been over a week now