Use First Name Last Name Instead Username

Hello,

This is a great plugin and I love this plugin so much. I need some modifications for this plugin. I want to change username on recipient into First Name and Last Name, so when user type the name of another users, the suggest box will not showing username but the list of user’s name that listed on database. Can you please help me?

Thank you.

https://wordpress.org/plugins/front-end-pm/