item.php
Line 348
replace
<?php if($mobile_found) { ?>
<a href="#" class="phone-show" data-item-id="<?php echo osc_item_id(); ?>" data-item-user-id="<?php echo osc_item_user_id(); ?>"><?php _e('Show', 'veronika'); ?></a>
<?php } ?>
==========
by this
<?php if(osc_is_web_user_logged_in()) { ?>
<?php if($mobile_found) { ?>
<a href="#" class="phone-show" data-item-id="<?php echo osc_item_id(); ?>" data-item-user-id="<?php echo osc_item_user_id(); ?>"><?php _e('Show', 'veronika'); ?></a>
<?php } ?>
<?php } else { ?>
In order to contact seller you must log-in first.
<?php } ?>