cannot use DISTINCT with WITHIN GROUP in Postgres

I am trying to make below query compatible with Postgres, which is originally written for Oracle select concat(s.udise_sch_code ,tch.teacher_id) comp_id, s.sch_id as sch_id, s.udise_sch_code as sch_code, s.school_name as school_name, v.latitude as latitude, v.longitude as longitude, tch.teacher_id as tch_id, tch.name as tch_name, tch.social_category as social_cat, to_char(tch.startdate,’yyyy-MM-dd-HH:mm’) as startdate, **LISTAGG(DISTINCT phone_no, ‘,’) WITHIN GROUP (ORDER BY phone_no) […]