Hi Michael, I have just tested this set up and unfortunatly the phantom will not forward the call to a busy destination the call remains ringing the phantom, so this setup will not work to return busy to the caller.

so we come to the point of wanting to see the DDI description so you know how to answer the call.
In station flags you will find a flag called
"Outside Party call information has priority"
Setting this flag to no on the phones which the agents log into will display the DDI description and not the calling party number.
If you need to see both then you have an issue with returning busy tone.

So to return Busy to callers when no agent is available, route the DDI to the group and set campon to no, set Outside Party call information has priority flag to no on the endpoints.

NB. If you do need to see the CLI of the caller you could use CTI app phone manager to achieve this.

Tim