Refund Refused at the till point !!!

Required a SDS chisel bit and - no stock , yet there was a sharp point concrete breaker , asked if it was SDS - answer yes , just after pying at the till point I noticed it was a SDS Max , before leaving the store , on requesting a refund , I was refused to be refunded !!! Had to accept a voucher with no other choice and with regards the matter on hand when I informed them that I am not happy and due to this specific incidence it is highly unlikely I would ever want to return to the store was not even responded to !!! So 300 Bucks tied up in a voucher for the item I needed and can not be used somewhere else other than the place that does not have it !!! Angry and my hard earned money in a place I do not want to use !! Will pursue this further - I want my money back !!!! As far as I am concerned this is trying to force me to spend money there regardless the fact that it is now the last place I would ever want to spend any time or money with .