We have a team that will rotate between phone calls and chats. Everyone is part of the phone inbox but they switch themselves to conversations only when they are not scheduled to be part of the phone calls. We have found that if all agents on the phones are not available, the VM will then route to anyone on the team even if they are not set to accept phone calls as it seems VMs are treated more like a conversation.
We would like it, and it would seem to make sense, that a VM stays only with those agents that are on the phones and continues to deliver to those agents when they do become available rather than go to someone who should be dealing strictly with chats