Report Abuse – Change Subject / Heading

Hi,
You can do it using filter hook. Add following code in child theme functions.php file –

add_filter('rtcl_email_heading_report_abuse', function(){
    return esc_html__( "Heading text here", 'classified-listing');
 });
add_filter('rtcl_email_subject_report_abuse', function(){
    return esc_html__( "Subject text here", 'classified-listing');
 });

Thank you