Bad attitude to customer due to staff incompetence

I bought two camping chairs priced R545, and was charged at the till R699. I immediately pointed this out. then waited. I was finally given a discount voucher *** and I was told to queue for help at exchange , I told them that why should I be penalised as a result of their mistake certainly they should help me and not expect me to queue ? I got other commitments and has no intend to wait. they are wasting my time, and I am not at fault. If I was returning or exchanging something I would understand. The sales manager blatantly refused to help me and rather allowed for a scene to be caused. So much for Game's image. He even told his staff not to assist. I left the shop on my arrival home I noticed the voucher is only valid for one day!! It is dated 3/2/15??? Today is already 4/2/15 , I cannot resolve this problem tomorrow or any other day I have already loosed my R310 ! I phoned their Store Manager Israel who promised that he will get back in five minutes this is more than a hour ago. I insist that they should apologise and ensure that I get my CASH back on this transaction. The service I received after their blunder is appalling and a disgrace to Game country wide