FNB *****ing my money

FNB have been non responsive to my communication with them in regards to my personal loan I had with them. After numerous attempts to contact them and get to the bottom of my issue, I have given up on them or their ability to assist me. They over charged me and when asked about it,they keep dead quiet. Instead, they add interest on my loan. I paid the balance of R371 and immediately after settling the loan,an interstate of R50 was added. IMMEDIATELY after I settled bare you. Then to my surprise, an additional R463 was debited from my account AFTER I SETTLED!!!No one can explain this nor are they willing to get back to me after an email I sent on 09/10/2020. What kind of service is this from FNB. Why am I being charged after I settled my loan?? What is the extra R503 for????my lunch is at 13:00,dont call me before or after as I wont be available