Use a different invoice template for orders with company field

functions.php

<?php

add_filter( 'storeabill_invoice_get_template', function( $template, $invoice ) {
    $template_id = false;
    
    if ( ! empty( $invoice->get_company() ) ) {
        $template_id = 320; // Post id of the template to be used
    }
    
    if ( $template_id ) {
        if ( $template = sab_get_document_template( $template_id ) ) {
            return $template;
        }
    }
    
    return $template;
}, 10, 2 );