Identity Miscalculation, sarcastic and abrasive attitudes

I am disgusted with Identity's customer services. Firstly let me outline our sequence of events:

My sister and I had just recently lost our father and was in the process of preparing his funeral arrangements. On Friday the 20th September we had gone into the Liberty Promenade branch and had queried a previous payment done on the 18th August 2019 and queried on the 30th August 2019. 1. Firstly my sister had an outstanding balance of R305.00 on her account of which she had made a payment of R200.00. Which leaves an outstanding balance of R105.00. 2. However the cashier had then punched in an incorrect amount of R305.00. 3. They then proceeded to "correct the miscalculation" but stuffed up big time. 4. She was then told by the staff manager that they would reverse the incorrect transaction and the correct outstanding balance would reflect by Monday 2nd September 2019. 5. This was still not corrected by Monday the 2nd September 2019. 6. She then returned on the 16th September and was assisted by the staff and area manager, once again a total miscalculation from their side. 7. One additional purchase was done on the 30th August 2019 for an amount of R180.00. 8. I fail to understand how and outstanding balance of only R105.00, plus an added amount of R180.00 ended up with a total outstanding balance of R475.00. 8. According to my calculations this should only have been an outstanding balance of R285.00. 9. She has queried this on multiple occasions with no success. 10. As far as I'm concerned, interest does not apply in this instance. 11. We have supp**** the area manager with all the subsequent receipts and have had no success or telephonic responses. 12. Your store manager and area manager requires a lesson in client servicing etiquette. As I've mentioned we had lost our father on that given day and gotten an unpleasant, sarcastic attitude.