Abstract: A computer-implemented communications device in communication with a transaction gateway server during a point of sale transaction. A computation server configured for intercepting a first transaction instantiated by the communications device, the first transaction having a first numerical value; the computation server instead of processing the first transaction processing: a second transaction having a second numerical value greater than the first numerical value, and a third transaction having a third numerical value determined based on a numerical difference between the first numerical value and the second numerical value.