سَلَّمْتُ عَلَى الدَّاعِي: I greeted the caller.
سَلَّمْتُ: past verb with subject tāʾ; عَلَى: preposition; الدَّاعِي: genitive noun with estimated kasra because of heaviness.
Three cases: الدَّاعِي (nom.), الدَّاعِيَ (acc.), الدَّاعِي (gen.). The rule matches الْقَاضِي.