Double debit

FNB deducted my debit order for the month of June on the 28th of May and I got a payment on the 4th of June and another debit went through. When I contacted them to ask why I was debited twice they told me to contact the service provider to refund me! To start with, my obligation to pay is with Fnb so hoe can they allow any company to take money from my account at any time they want? Now I'm R2768 short in my account all thanks to Fnb

I'm so disappointed in their service