FORTUNE -- Call-center customer service has become a finely honed discipline, but usually it seems honed to cut time: The agent is superficially friendly, but nothing can derail that person's mission of getting you off the phone fast. Service at American Express (AXP) wasn't much different from that before Jim Bush was put in charge of it in 2005. His basic insight was that breaking with industry orthodoxy by transforming those conversations into less structured, more human engagements would pay off. Instead of evaluating service reps mainly by how quickly they got you off the phone, as many companies still do, he switched to the net promoter score developed by Bain's Fred Reichheld. It's based on one question: Would you recommend this company to a friend? AmEx's score has risen significantly under Bush's direction, and he was right -- it pays off. Customer spending is up, attrition is down.
Bush, 54, majored in accounting at New Jersey's Rider University. As AmEx's executive VP of world service, he oversees some 20,000 employees, about a third of the company's total. He talked recently with Geoff Colvin about how the company has changed the way it trains service employees, the power of personality, turning collection calls into positive experiences, and much else. Edited excerpts: