To create acceptable levels of Quality of Service (QoS), designers need to be able to predict users’ behaviour in response to different levels of QoS. However, predicting behaviour requires an understanding of users’ requirements for specific tasks and contexts. This paper reports qualitative and experimental research that demonstrates that future network service must be based on an old principle: service and its associate cost must represent value in terms of the contribution it makes to customers’ goals. Human Computer Interaction (HCI) methods can be applied to identify users’ goals and associated QoS requirements. Firstly, we used a qualitative approach to establish the mental concepts that users apply when assessing network services and charges. The subsequent experimental study shows that users’ require certain types of feedback at the user interface to predict future levels of quality. Price alone cannot be used to regulate demand for QoS.