Use text like this to introduce the participant to the kind of research you are doing, as well as the format of the interview.
Thank you for your interest in the research project at [company name]. We are going to interview [number] people from around the [nation/globe], representing various [topic of scope] roles. You have been selected because of your role and because of your interest in furthering understanding between everyone involved in [the scope]. Our interview will take 60 minutes. We are interested in hearing you talk about the way you approach [topic of scope]. We want to hear the details of how you make decisions or solve certain situations. We are interested in all of your decisions, no matter what tools you use to carry them out, no matter what vendors you interact with.
We are delighted to have you participate in our research, and we look forward to meeting you on the telephone!