We want to train a customer support person in another state. We have no soft phones, or voip phones in our system. Access to RC is via cell phones only. When a call comes in to a trainee, we want a supervisor to be able to monitor the call and then break in if necessary to help the trainee. Can we do that without physical phones? If necessary, we would buy physical phones for the supervisor and trainee. What would we need to buy? Thanks.