Hey Jellybean! Sounds like a fun survey project. When doing in person interviews, like having senior managers contact customers directly poses different challenges than surveying through an automated email list or pop up campaign. Most notable would be a stronger amount of ‘social desirability bias,’ or in other words people trying to give the answer the interviewer would most approve of. Another source of bias could come from the different interview styles of the managers, like different levels of professionalism or happiness during the interview.
You may want to go the route of the mass telesurveying style, by forcing a strict process on the respondent selection and how the manager can interact with their respondents.
Hope this helps!
The attention grabber you use is up to you, but here are some ideas: