Poor customer service

I accidentally transferred funds from my cheque account to the CBS account, I contact FNB immediately I was sent from pillar to post some of the consultant were rude, they finally gave me an email address to send my query of which I did I stated all my reason and requested a refund, it literally takes more than 3 days before I get a refund, there after I'm being told it will take up to 7 days to get my refund, I don't understand because I'm bank with FNB how does it takes to pay a refund in 7 days whereas it should be instantly if is with the same bank ?, The service that's given to black customers is really poor and frustrating, I highly don't recommend anyone to bank with FNB