Incorrect change

It has come to my attention that pep cell store - promenade mall, Mitchell's plain particular, do not give the customers correct change when buying something like airtime. It serve no purpose if the Pep provide discount airtime, but does not return the correct change. A few cents may be nothing, but if you accumulate it over time, it all adds to more than just a few cents. I think staff is too lazy, to prepare a proper cash flow.