Style and price are the two biggest reasons why consumers choose a particular mobile phone, according to a survey by J.D. Power and Associates.Thirty-nine percent of the 18,740 users surveyed mentioned design as a buying factor, making it the single most popular answer, according to Kirk Parsons, an analyst with J.D. Power. Getting something for nothing was the most-cited cost factor: 29 percent said they chose their phone because it was free.Few respondents said they chose their current phone because it had a particular feature, such as a color screen, a digital camera or speakerphone.U.S. consumers have been slower than those in many European and Asian countries to embrace advanced mobile services and the feature-rich phones that support them. However, consumers\u2019 use of advanced features is gradually growing. Use of the most popular special feature, speakerphone, rose from 22 percent of respondents last year to 26 percent this year. Also in the latest survey, 19 percent said they use a camera phone regularly, up from 14 percent previously.