Double billed ,Negligence and poor systems

this evening i went into shoprite to return a pack of mashmallows because it had holes when i got home it seemed as though it was eaten by rats ,fine good and well the pack was exchanged without a hustle however i had to take time out of my schedule to return that item because of negligence,anyway while at the shop i decided to buy some items amongst the items there were g***** that were originally r18.99 however were marked down to r10.00 a supervisor by the name of Catherine was called to come and override to the reduced amount needless to say this excercise is also quite irritating were you as a company decide to put something on reduced amount and not make it such that it automatically scans the new amount but then those are your processess ,i got home i checked my slip and realised that i was charged r18.99 as well as the reduced amount of r10.00 in other words i was charged for one item two different amounts.This is quite IRRITATING as i do not stay around jabulani and now because of your systems and somebodies negligence i might be forced to spend more that the r18.99 to go get my incorrectly charged amount .VERY BAD SERVICE THAT SHOPRITE IS RENDERING TO US CUSTOMERS.