Accepting a quest from a payphone is one of the first challenges you can complete in Fortnite Chapter 2 Season 7.
Like NPCs, payphones allow you to accept quests which will reward you with Gold Bars, which, in turn, can be spent on weapons and helpful services from NPCs.
Completing this challenge will reward you with 30k XP, which will help you unlock more Battle Stars for the Season 7 Battle Pass.