First ensure that your did provider is sending  country code plus the number in the e.164 format.  eg 1 785 823 8284 for US number.

If your device is registered and the number is ringing busy, you may need to do the following :-
  • Ensure that the NAT Keep Alive interval  parameter in your Linksys or voip device is set between 30-50 seconds
  • Disable ALG
  • Disable port forwarding on your NAT router
  • Ensure your firmware is upgraded to the latest provided by the device manufacturer.
For those using Voice Mail On PortaUM
If you are on using PortaUM, please add the PortaUM tariff in the product accessability node and add prefix UM in the reseller and customer tariffs.
Thank You.
Globalink-Worldkom VoIP Services
http://support.globalink.us