We consider an M/M/1 high-contact service queue with unknown service rates. Two types of customers, informed and uninformed, making strategic balking decisions, queue at the facility. We find that informed customers follow a threshold strategy and uninformed customers follow a non-threshold strategy in equilibrium. We suggest that the firm should incentivize the fast server such that the quality of service is not compromised. © 2021 Elsevier B.V.