hook_post isn't called deleting an activity

As the title says, the hook_post isn't called when I delete an activity.

function civicrm_phonecampaign_civicrm_post($op, $objectName, $objectId, &$objectRef) {
if ($objectName == 'Activity')

{ CRM_Core_Error::debug_var('op', $op); }

}

That code doesn't log anything when I'm deleting. It's logging ok when I create an activity.