American Express has come out on top of this year's JD Power credit card satisfaction study.JD Power asked consumers to rate their cards on six measures: interaction; card terms; billing and payment; benefits and services; rewards; and problem resolution.On a thousand-point scale, Amex scored 755, followed by Bendigo Bank (748 points) and Coles (737 points).Among the big banks, Commonwealth Bank scored 721, National Australia Bank 719, Westpac 705 and ANZ 692. Woolworths was lowest ranked with 678.JD Power said in a media release that scores were up on last year. However, 20 per cent of survey respondents felt that the value of their rewards had declined over the past 12 months. JD Power said poor perception of rewards programs tended to affect spending."Australian consumers are not getting enough from the loyalty and rewards programs offered by credit card issuers or simply don't know how to access the benefits or understand them," it said.Half the respondents were unable to recall a single benefit that comes with their cards. The most popular rewards are gift cards, airline tickets and cashback offers.The most common reasons for switching credit card issuers are to avoid paying annual fees, to get a better rewards program, a lower interest rate and better benefits.