Charged for requesting proof of banking details

I went to the bank to request proof of my banking details and was told that I would have to pay R50 to receive them. A piece of paper with a stamp now costs me R50. Nobody informed me of this NEW charge, I asked to be shown where it is written and the staff member could not furnish me with such a policy. However I was still billed for it without my consent. Why am I being charged for confirmation of banking details if the bank is the only place I can go for confirmation???? This is unfair. Standard bank needs to tell me why I am charged for this.