Personal communications such as phone conversations, private letters and interviews are not included in your reference list.
If including emails or personal communications in your reference list, no title is needed. After the author add the phrase, private communication.
[1] Author, private communication, Abbrev. Month, year.
[1] G. Rowe, private communication, Jun 2021.
When using another person's ideas or words, include an Arabic numeral in square brackets (consecutively numbered).
... has been recently identified. [1]
... the effect of electromagnetic radiation [1] on humans has caused much debate over the years.
If you are making a direct quotation, use quotation marks.
Archer [1] stated that "gas hydrates on the Hikurangi Margin may be of commercial interest."