Double debited and incorrect debit dates

I'm really frustrated with Nedbank lately. Firstly you debited an amount before time and I had to reverse the debit order because I needed funds. You then debited the funds on the 15th and another debit order went through today on the 19th. I've always stuck to my payment arrangement and I don't understand why are unauthorised debit orders going through in my account. May I please get a refund for the extra funds you debited in my account. I can't keep going to my bank to reverse the funds cause there's bank charges involved. Stop it!