A trade management device transmits, to a portable device, a request of decreasing a minimum price corresponding to the minimum trade unit of the trade object from a remaining value associated with the portable device. A controller provides the trade object by the minimum trade unit when a response to the request from the portable device indicates that the request is successful. A determiner determines whether the next providing of the trade object is possible on the basis of the providing status of the trade object. When a determination that the next providing is possible is made, the next request of further decreasing the minimum price is transmitted to the portable device. When a determination that the next providing is not ready is made, the trade is ended without a transmission of the next request.

Embodiments provide methods and systems for controlling payment transactions in a payment card using a companion payment application installed on a user device. The payment application and the payment card may be provided by an issuer server. Using the payment application, the number of transactions allowed on the payment card or an amount limit is set for the payment card. The payment application is used to set, reset, change the value of a counter in the card, which determines the number of allowed transactions. When the user attempts to make a transaction at a POS terminal, the payment card reads the value of counter, and if the value is not equal to a threshold value, the payment card exchanges data with the POS terminal and updates the value of the counter. The payment card is precluded from transaction when value of the counter is equal to threshold value.

Embodiments described herein provide a client system for facilitating enhanced offline payment. During operation, the system obtains a location indicator, which indicates the location of a service, from a charging system. The system then generates an offline code that allows access to the service and corresponds to the location indicator. The offline code can be readable by the charging system, and the client system and the charging system can both be offline. Subsequently, the system encodes the historical data associated with the service in a field of the offline code and sends a message comprising the offline code to the charging system.

A printer credit management method is disclosed, the method includes receiving a code at a printer. From the code, a printer identifier and a credit value are discerned. It is determined if the printer identifier corresponds to a unique identifier assigned to the printer. Only upon a positive determination, a credit balance maintained by the printer is updated to include the credit value.