How to fix: outlook showing wrong contact infomration - How To Reset The Outlook Nickname Autocompletion Cache on a Mac

It took me a while but this article solved my problem: 

ON a PC:

To delete a single cached entry:

In Outlook:

1. Open Outlook.
   • Outlook 2010/2013/2016/2019: On the Home page, click New Email.
   • Outlook 2007: Click New > Mail Message.
2. Type one or more letters of the recipient name or address; this will show memorized (cached) entries in a drop-down list.
3. Use the arrow keys on your keyboard to select the entry to be deleted. With the entry highlighted, press the DELETE key on your keyboard.
   This removes the entry from your autocompletion cache.

On a Mac:

In Outlook for Mac 2011/2016:

1. Open Outlook and click New email.
2. Type one or more letters of the recipient name or address; this will show memorized (cached) entries in a drop-down list.
3. Use the arrow keys on your keyboard to select the entry to be deleted. With the entry highlighted, press the DELETE key on your keyboard. Or you can click on the cross sign with your mouse.
   This removes the entry from your autocompletion cache.