Using cell phones in surveys poses new challenges to survey researchers. Amongst others, high proportions of nonworking numbers in randomly generated cell phone samples are reflected in increasing survey costs and extended fieldwork periods. In addition, ambiguous voicemail and operator messages which do not clearly indicate the status of a number negatively affect the proportion of numbers of unknown eligibility as well as the reliability of response rates. The simulated experiment reported in this article aimed at increasing the proportion of working cell phone numbers in the sample by screening out technically invalid or temporarily inactive numbers prior to fieldwork. Two methods were tested: number validation and text messaging. Findings from the application of different screening rules varying in strictness show that pre-call validation increases working number rates whereby survey costs and numbers of unknown eligibility can be reduced. Strict screening seems to be more efficient, however, at the expense of higher screening error.