REUSE TO REFUND ME MY R615.00

I have been going back and forth with FNB for a reversal of my money they deducted twice from my account. More than 5 working days has passed and they absolutely refuse to refund me. I have provided the Bank with all the information and proof that the fault was on the banks side but I am being sent from pillar to post. I am disgustingly disappointed in your service as I have been banking with you since I was in High School. I will write a ROTTEN REVIEW about this bank EVERY SINGLE DAY until you refund me my R615!!!!!!!