Multiple Types of Data Collection
QSP is qualified to collect information from different types of data collection to the same study: Telephone, online, face-to-face or others. In some cases it is useful to collect information using different methods. We are talking about perhaps in very specific targets, very hard to access.
It may be useful first contact via phone, where they perform a series of initial questions, and then route respondents to complete the survey in an online platform. This method is still widely used when a follow-up interviews is requested.