A method for controlling payment in a communications system including the steps of providing a service accessing a service provider from the or one user device, selecting a product for purchase from the service provider, the service agent receiving a request for payment from the service provider via a payment operator and the service agent issuing a payment authorisation to a payment provider via the payment operator. The service agent is installable in a variety of user devices and provides a uniform interface to the payment system from a plurality of the user devices. The service agent may also provide a uniform interface to an ordering system from a plurality of the user devices.