How do I refer to a telephone interview and should this be included in a report?

As the reader cannot consult the interview, the in-text citation refers to it only as personal communication.

It is not compulsory to draw up a report and include it as an appendix, unless it has been indicated in advance that this is required. If an interview transcript is included as an appendix, 'personal communication' is replaced with a citation of the attachment, for example: (see Appendix A).