Sometimes it is necessary to set the ISDN calling number plan type to national or international to have calls pass successfully through a carrier.
Consider translation rule four set on the gateway, as shown:
translation rule 4
rule 1 ^4 9004 international international
rule 2 ^4 904 national national
translate calling 4
Perform these steps:
Match any calling number beginning with the number 4 that has national or international carried across the VoIP network.
Set the ISDN plan type for these numbers to national or international, respectively.
Additionally, prepend national numbers with 90 and international calling numbers with 900. In this case, the call is being placed through a PBX. An access code of 9 is used. National numbers are prepended with a 0, while international numbers are prepended with 00.