1) Addressing and understanding the concerns is the first step
The biggest mistake you can make is preparing a solution before getting on the phone. In many cases, you don’t know what the customer expects as far as a resolution, so offering them a refund or discount may not be appropriate and could make the situation worse. Instead, listen to their complaint and ask them what they think a fair resolution would be and go from there. If you can meet what their expectations are, they’re going to feel a lot better getting off the phone.