Unfair treatment of account applicant because I did not use their credit card.

I app**** for an Account Card at Queenspark. My application was turned down because RCS who is their Credit Provider did not think I was worthy because I have had a RCS card with a credit limit of R15000-00 which I have not used. My question is how can they make a judgement based on that. I have other clothing account cards which are active and accounts are paid on time. My suggestion is that they can keep the card. Maybe give the card to someone who does not pay their accounts. Queenspark has lost customers and now they can lose more custromers. Do not buy from them at all I wont even if I want to.