At the Social Science Research Institute (SSRI) we manage a call center which we use when data is collected by phone.
Interviewers under the aegis of the SSRI get specialist training and a thorough introduction to the project at hand.
The interviewers follow strict operational procedures that guarantee neutrality, consistency, and quality. In addition, a project manager supervises each project. The project manager works closely with interviewers and during data collection, reviews a selection of the responses to ensure data quality throughout.