Bad customer service

A worse customer service I received today, I made a purchase of R1366 and the till requested Me to an amount of R10. 60 I asked why, they I have been randomly selected a worn my grocery for free, the cashier called her supervisor, they aborted the transaction and requested to rescan my whole grocery again without any explanation, I was highly disappointed and call for management for explanation, but I didn't get one, shame on shoprite