OS in Lower Court frustrated WP

Dear Members,

A Writ Petition while in existence, 3months later the defendant filed OS in a Lower Court. On subsequent date referring the OS in his counter in Writ he got the Writ dismissed. In the Writ Appeal even after producing copy of Plaint in OS to prove that the date of the OS is subsequent to the WP the Court rejected the WA. What legality is in this? Whom should I approach for further justice?

Thanks!