FNB Personal Loan - System Glitch

FNB is generally pretty good - but when something goes wrong it's always hard to get it fixed. Call Center escalated and said they'd phone back - but nothing. Here's the story :

I took a personal loan on the 20 September the debit order has come off Oct, Nov and Dec as normal. Additional to this, I paid extra *twice* in November and *twice* in December. In other words 7 payments in 3 months. But here are the queries :

* After all these additional payments, it's telling me I'm in arrears with loan (this is a debit order anyhow)

* The debit order amount which will come off January is different (?) on the app and the website

* Unsure why the December debit order was mid month ? And I thought we skipped January ? I don't care - but it shows your system isn't working ....

I need to remove this arrears amount and sure it hasn't effected my credit score now ; I need to find out what the real January debit order actually is (if there is?) - and now I'm also doubting the calculations / interest as well? How correct are all these figures?