FNB IS A GREEDY LOAN SHARK

I transferred R1210 into my loan account as a settlement amount on the 14th of December. FNB still debited an instalment amount of R496.68 from my easy account on the 14 of December without my authorization. My loan agreement states that they will debit my account on the 25th of every month until the balance is paid in full. Given the fact that 25 of December is a public holiday, the debit date should have been brought forward to the 23rd of December. The FNB app showed that they will debit my account on the 23rd of December. But the minute there was funds on my account they went ahead and debited my account the full instalment despite my account being paid in full. I want to know why and who authorised them to do that. Therefore, FNB has breached the loan agreement. Furthermore, the balance on my loan account is showing zero when it is supposed to be in a credit balance of R496.68. I sent FNB a message via the app and still response. I want to know who authorized you to debit my account on the 14th when the agreement is on the 25th monthly? Also, where is my money R496.68 you debited from my account? FNB id quick to debit yet slow to resolve their mistake. You never make errors when you benefit and yet don't care when the the client is inconvenienced. I am left with no funds as I had made plans on how I was going to use my money and today I don't have enough funds. I want you to pay interest on the R496.68 that you owe equivalent to the interest you charged me in my life account.