我想发送短信到号码存储在一个 JComboBox 但不工作会使系统冻结。但是从中获取电话号码 JTextField 正在工作，但从组合框中获取不起作用，并引发以下错误：

15:12:54.672 [AWT-EventQueue-0] ERROR smslib - GTW: : CMS Error 500: 
Quit retrying, message lost...

短信发送者应用

AbstractTester at = new AbstractTester() {
    @Override
    protected void test() throws Exception {
        throw new UnsupportedOperationException("Not supported yet."); 
    }
};

OutboundNotification outboundNotification = at.new OutboundNotification();
SerialModemGateway gateway = new SerialModemGateway("", cmbPorts.getSelectedItem().toString(), 9600, "", "");
gateway.setInbound(true);
gateway.setOutbound(true);
Service.getInstance().setOutboundMessageNotification(outboundNotification);
Service.getInstance().addGateway(gateway);
Service.getInstance().startService();

for (int i = 0; i < cmbNumbers.getItemCount(); i++) {

    OutboundMessage msg = new OutboundMessage(cmbNumbers.getItemAt(i), smsArea.getText());
    Service.getInstance().sendMessage(msg);

    txtAreaLog.append(msg.toString());
    Service.getInstance().stopService();
    Service.getInstance().removeGateway(gateway);

    JOptionPane.showMessageDialog(null, "Your Message has been sent successfully to:" + cmbNumbers.getItemAt(i) + "");
}