If you want to cite an interview, email or other personal communication, you only need to do so in the body of your paper; you do NOT need to include it in your References.
Include the date of the communication and how it was documented (letter email, document).
Accepted formats include:
According to a letter from B. N. Pence, in September 2019, ...
Similar findings have been noted by B. N. Pence (email, September 15, 2019).