A method of delivering a service from a service provider to a customer in a network system comprising a plurality of service providers and a network control and provisioning system through which connection of the customer and service provider is controlled, the method comprising: connecting the service provider to the control and provisioning system via a service manager application which contains predetermined values of conditional data parameters for services to be provided to the customer; on receipt of a request from a service provide to provide a service to the customer, interrogating the customer's connection to the network by means of the service manager to determine the current values of the conditional data parameters and comparing the current values with the predetermined values to determine whether or not conditions for provision of the requested service are met; and communicating the result of the comparison to the service provider to either confirm the requested service or to indicate which of the conditional data parameters does not meet the conditions.