fauls information to attract customers.

I opened a Foschini account in Jan this year, i was given discount vouchers to use on specufic dates. I have a R200 discount voucher to be used when I make a purchase on my account for R600 or more. Today I get in to a total sport outlet 2 buy a pair of shoes for R749. To my surprise, the teller by the name of Wayne refused 2 process my purchase saying according to their system, I have to make a purchase of R800 or more in order to redeem my voucher. I argued with the Teller as that is not what was written on the voucher. Then we decided to call FG call center which the agents tend to hang up on us after explaining the challenge we had. Until 1 rude lady by the name of Afo decided to listen to us. She then told me that its either I make a purchase of R800 in order to use the voucher or I should just leave the store as I dont know what I want. All I want to know from FG is that, why are they selling faulse information to customers? The agents and tellers are so rude and the service they are rendering is bad. I need this to be escalated and I want be informed why they sold faulse information to me?