According to one aspect of the disclosure, there is provided a method for conducting a transaction between a service provider and a merchant, the method comprising: issuing an account number against which a transaction with the merchant is made, wherein the account number belongs to a subscriber registered with the service provider; assigning a unique reference used to map the subscriber to the account number; and transmitting, upon receiving use of the account number for the transaction, the unique reference and details of the transaction to the service provider, wherein the unique reference is processed against a database of unique references to identify the subscriber to which the account number belongs, for the service provider to associate the transaction to the identified subscriber, based on the details of the transaction. A service provider server, a server network and a system that implements this method is also disclosed.