Which process is responsible for dealing with complaints, comments, and general enquiries from users?

Service level management negotiates, monitors, and reports on service level agreements; it does not handle individual user complaints or enquiries.

Service portfolio management governs the full set of services managed by the provider across their lifecycle and has no role in processing individual user communications.

Request fulfilment is the ITIL process responsible for managing the lifecycle of all service requests from users, which explicitly includes handling complaints, comments, compliments, and general information enquiries. It is distinct from incident management and provides a channel for users to communicate routine needs without raising a formal incident.

Demand management analyzes and influences customer demand for services to ensure the provider can meet it; it does not process user complaints or enquiries.