Abstract: The disclosure is related a payment-by-proxy service that receives a payment request made by a joint payment card and processes the received payment request by a primary payment card linked to the joint payment card through a payment card processing system including, user devices, a payment terminal of a merchant, a service server of the payment-by-proxy service, and financial institution servers associated with the payment card and the primary payment card. For such a service, a payment card may be configured to store an identification data used for requesting a payment and an initiation data used for processing a payment through the payment-by-proxy service, to generate an initiation message based on the stored initiation data upon receipt of a request signal for the identification data from the payment terminal, and to transmit the generated initiation message to the payment card processing system in response to the request for the identification data.