Issue with the calls going into the queue just before the lunch break

The default behavior is to use the default Customer Queue flow that play prompts until someone picks up the call

https://docs.aws.amazon.com/connect/latest/adminguide/set-customer-queue-flow.html

What you need to do is add the Set Customer Queue flow block in your flow before Transfer to Queue block. And this is where you can specify the Sample Callback Queue flow, or create your own customer queue flow to check on different condition to do different action like transfer the call to voicemail, disconnect the call, etc.

One trick is how long to play the prompt before asking them or checking these conditions, if you look at the default customer queue flow, there is only one block https://docs.aws.amazon.com/connect/latest/adminguide/loop-prompts.html

In there is a way to check timeout to break the loop prompts block and check. Be careful that once the check is done and go back to Loop Prompts, it starts again instead of resuming where the prompt is left off prior to the break

You could adapt the Sample interruptible queue flow with callback. Instead of checking for customer input, you can check on queue status and then tell the customer that there's no agent available and therefore give them a callback option.