Let's face it: Service contractors get phone calls from irritated people because the customer on the other end is usually: a) very hot or b) very cold. Usually, an untimely breakdown has happened, and the caller's panic button is on full alert.
From this point, the service you provide can either soothe - or increase - these feelings of panic and irritation. That's why a better understanding of common complaints from customers about contractors can help you a lot. But some bad news first.