Single Call Handling for users that are working Queue Calls.

We have users that are what we call "Customer Service Reps" Primary function is to take inbound calls from the queue, while they won't get presented a second call from a queue, they are getting interrupted by DID calls and Transferred calls, this really kills their work flow and focus, having to ignore or send to voice mail calls that come in while they are working a call. I have administered 3 different phone systems over the years and this is the first one that did not have call handling, and I would really like to see it as a check box on each extension. TKS