Very poor and rude behaviour to a customer

Today I found a supervisor at Pick n Pay Knysna's behaviour totally unacceptable.

I was making a purchase and one lot of the items were marked 3 for 2, but the items all charged full, with none free. When I questioned this with the cashier, I was told that I need to swap one of the items with something cheaper in order to get it free. I responded that surely that was not correct, but twice I was told that is the case. Being made to feel like an idiot I asked for the supervisor to be called, because that is not correct.

The cashier called several for the supervisor numerous times. He pretended to not hear her, whilst looking straight at us. A friend who I had been with was waiting at the Money counter where he was standing, and when the lady behind the till informed him he was being called, when he rep**** the customer must wait he is busy. He repeated this a second time when he was urged by colleagues that a customer needed attention.

I see this is very poor service and would like to know how this behaviour will be dealt with. In the company where I work there will be severe repercussions for this kind of insolence toward paying customers, who ultimately pay their salaries.