Be sure that you have your DIDs and users configured. In this example, we will use testuser as the username with a phone number of 4158867999 and our domain is my.phoneco.test.

Create a dialplan extension, specifically for handling calls to the DID number and use some regular expression syntax to parse out the information. Here is an example:

<extension name="call_4158867999">
  <condition field="destination_number" expression="^\+?1?4158867999$"/>
  <condition field="${sofia_contact([email protected])}" expression="^[^\@]+(.*)">
    <action application="bridge" data="sofia/external/4158867999$1"/>
  </condition>
</extension>

You would typically make bridge calls to testuser using the bridge command with an argument of user/testuser. In this scenario, however, you wish to call testuser's registered endpoint but replace testuser with a phone number – 4158867999, in our example. To do this, you must retrieve testuser's current dialstring and remove the username, replacing it with the DID number.

In the example, we leverage the sofia_contact API and some regular expression magic. The first condition simply matches the user's DID phone number—we only want to act if the destination number is 4158867999. The interesting stuff happens in the second condition. The field is ${sofia_contact([email protected])}. By wrapping an API call in ${}, the dialplan literally executes the API and uses the result as the field value. If we go to fs_cli and type sofia_contact [email protected], we get the result, which is something like this:

sofia/external/[email protected];fs_nat=yes

The regular expression pattern ^[^\@]+(.*) is applied against this value. The result is that everything after the @ is placed in the $1 variable. In our example, $1 contains @12.13.56.7;fs_nat=yes. Finally, we execute the bridge with the dialstring sofia/external/4158867999$1. With $1 expanded out, our destination is as follows:

sofia/external/[email protected];fs_nat=yes

We have successfully replaced testuser with 4158867999 while preserving the necessary IP address and parameters for contacting the server and sent the call to the proper destination.