Deliberate overcharging a client

On the 15th May 2024 I settled the account of the vehicle I had leased from Wesbank. To my surprise the settlement was very high for a vehicle I had been paying for over 2 years however I settled the account regardless. Fast forward to date I still receive an invoice from Wesbank every month showing an amount of R7180-11 that is unallocated clearly showing the money is due to me. In January 2025 I then took the liberty to send wesbank an email highlighting this error and furnished them with my banking details where they should transfer the refund due to me, i didn't get any response to my email to this day. I write this review because tonight 22nd February 2025 I just received an invoice from Wesbank of the same account that I settled in May 2024 showing once again the amount of R7180-11 which remains unallocated and in excess/surplus. If that is not enough the invoice I received tonight shows on the 1st June 2024 is was billed R4917-05 and on the 1st July 2024 I was billed R4917-05 and R2220-05 respectively,this charges comes even after the account was clearly settled on the 15th May 2024 and the Natis documents registered in my name and received by me show the vehicle is settled and mine. I had no idea wesbank would be so *********. According to my calculations wesbank owes me R7180-11 plus R12054-14(01 June and 02 July invoices) they erroneously included in my settlement.