What you are trying to implement is an inbound call center, right? You have two options, either you only use a queue in which you put the agents' extensions or you use the Call Center module.
If you use the latter, you too have two options:
- Callback Agents: You have to create the queue in PBX Configuration, put the agents' extensions there, then select that queue into the Queues (under Ingoing Calls) and then register those extensions in Callback Extensions (under Agent Options). In this mode, your agents get a call everytime a customer dials in to your PBX.
- Regular Agents: You have to create the agents in the Agents menu (under Agent Options), then create a queue in PBX Configuration and put the agents number there. In this mode, your agents have to be on a call with the queue the whole time with some music, and when que call comes in, the music will stop and the customer will be heard to the agent.