/**
  * send notify email for limit of sms credits
  */
 function do_sms_limit_notify()
 {
     // do something every day
     $sms_limit = isset($this->customizations['ws_sms_credits_limit']) ? $this->customizations['ws_sms_credits_limit'] : 0;
     $sms_limit_email = isset($this->customizations['ws_sms_credits_notify_email']) ? $this->customizations['ws_sms_credits_notify_email'] : '';
     $notify_status = isset($this->customizations['ws_sms_credits_notify']) ? $this->customizations['ws_sms_credits_notify'] : 'no';
     $current_sms_num = WC_Sendinblue::ws_get_credits();
     if ($notify_status == 'yes' && $sms_limit_email != '' && $sms_limit != 0 && $current_sms_num < $sms_limit) {
         $subject = __('Notification of your credits', 'wc_sendinblue');
         WC_Sendinblue_SMTP::send_email('notify', $sms_limit_email, $subject, $current_sms_num);
     }
 }