I would use my extensive experience with de-escalation and calmly work towards a proper resolution with this customer. For example; If a customer was requesting a manager, I would work towards that goal with them, but use these tactics to also get a little more information from then. One way to do this would be similar to this " I can definitely track down a manger for you, but while we are waiting for one to become available could you provide me with some background on what's going on so I can ensure it is documented today on your account?". After which I could use this as a starting point to ideally provide a resolution if I had one and avoid the escalation need altogether.