The entire process begins, from the customer calling on your service number to the call getting routed to an agent and is treated as one channel or line. So, One active call is one channel. You can select up to 1000 channels for your plan.
The customer has taken only one channel unlimited plan in the above example. Hence the first call shall be connected to the IVR Agent; the remaining calls are rejected and shown in the call log as Lost calls and assigned to the admin. You can call back those calls by visiting the Call Log report on the web and mobile apps.