Debit order dispute

A debit order of R2087 Rands from dialdirect off from my account. I have tried calling FNB to reverse the debit order to no avail. I have cancelled my car insurance with dialdirect and I am insured with oldmutual. I have went to the Newcastle branch to reverse the debit order but they couldn't assist me. As we speak my car is not insured as the wrong company which I cancelled my insurance with debited the money that was supposed to be paid to the current company i am insured with. I don't understand why it is so difficult to reverse the money back to my account. I was I advise to apply for the reversal on Covid 19 relief and they rejected my application. I am not applying for Covid relief I just want to reverse a debit order.