What I would do would be to have the back office team in a different group so they don’t have to be in a busy code. You can then build into the dialogue the function for the system to determine when you’re busy and when to transfer calls to the alternative queue.
I’m not going to take credit for this, the idea came from this forum, the instructions on how to build the dialogue were put in here by @JonathanRedsell.
They’re here Hints and Tips - Setting Queue Limits within a Dialogue
I’d set this up so that the calls divert to the back up team when it’s busy and calls can be transferred to them if needed.
Good luck