Rafael,
I think I'm going to need more information regarding what is meant by connected/not connected. Essentially all callbacks should connect with an agent at some point (unless for instance a callback is cancelled by an administrator). But maybe you are asking about which callbacks have an agent that eventually connects to the customer. I'm not sure that we have a report specifically designed to answer that question, but maybe it is something that can be obtained through analytics. If you could provide a little more detail on what you're looking for, I can try to answer the question more precisely.