There are 3 different places where you can setup a technical prefix:

1) In the Authentication Rule of every account (inbound traffic):

When you add a tech prefix to an Account's Authentication Rule it influences call routing.  The system requires the prefix in the Tariff Rate list and in the Destination Set of the Routing that the Account uses.

The following translation rule will add the 53872# prefix:

  • s/^/53872#/

See more rules in the following documentation:

Understanding Number Translation

2) In the Account properties for calls from those registered in an Account:

3) In the Connection Properties for outgoing calls to the Vendor 

In this particular case, the system adds a prefix for CLI or CLD numbers before sending a SIP request to the Vendor.