Chat/Claim Feature in my free item and Good Deeds App

I have an app called Karma Points, It rewards users for doing good deeds and giving away free stuff by giving them points to use in a brand discount marketplace. It is currently live: I am having issues with users when they click on an item in the free item section I would like there to be a way for them to directly message the users to coordinate pickup etc. Can someone help me with this?