A number of recent studies (e.g., Tucker, Brick, and Meekins (2006), Brick et al. (2007) Tucker, Brick and Meekins (2007), and Link at al. (2007)) have shown demographic differences among three groups of telephone users: • Landline-only• Landline plus cell phone • Cell phone-only In general, cell phone-only users are younger, more apt to be renters, more apt to be single or other non-family people, apartment dwellers. Much like them are those from households with both types of phones, but who use their cell phones most of the time. With the demographics of cell phone users now known, the question of interest to researchers is whether the dependent variables of a telephone interview research study would change if cell phone households were included, proportional to their incidence, in an RDD sample. The question has cost implications for research as well as methodological interest in any changes in dependent variables. The American Customer Satisfaction Index (ACSI) is a 14-year old measure of customer satisfaction of customers of 200 major companies that produce 60% of the GDP. Two of the measured companies, Wal-Mart and Target, were selected for the research because they have distinctly different types of customers: Wal-Mart: older customers with lower educations and income; Target: 35-54 year olds with higher incomes. The customer satisfaction of each (ACSI) was measured at the height of the 2007 holiday shopping season, with samples drawn as landline-only RDD numbers, and with a supplementary sample of cell-phone numbers. ACSIs were then compared for the three types of telephone user customers of the two companies. Sample efficiency and data collection costs also were examined.