A Review of the Sales Navigator App for iOS is a reference to an article on mapping contact information and grouping and dealing with them.
Link: A Review of the Sales Navigator App for iOS by Adam Young
(Note that I, personally, am an Android user, so I don’t have an Apple phone. Actually, any sales app can be used by a missionary, but I personally prefer and use TNT Connect which is especially designed for use by missionaries, including keeping their support and donations information, as well as reminders for thank you notes.)