OK I guess I got confused when you said "wants to send out her extension"
My advice still stands you need to first check what you are sending if you think the system is configured correctly.
How you configure the system also depends on what the carrier is expecting.
At a basic level you can either use "Internal data" which is the number under the SIP tab of the user or you configure the outbound caller ID on the SIP URI under the SIP line Call details TAB.
Or a combination of both depending on your requirements. If you have a hight percentage of users that want to display, their DID as the outbound callID then Internal data is best.
Set the required number under the User SIP tab and then setup the SIP line Call Details to allow this to work.
What I do is create two entrees Under the Call Detail tab, the first is for incoming calls with the incoming Group as 1 and the outgoing as 99 (It not used). This will be used by the system to accept all incoming calls and process them as per the incoming call route
View attachment 862
Ill then load a second entree fir outbound call to use the "Internal data" of the user SIP tab for the outgoing call. This example also has the settings our default carrier requires for A party on twinned calls.
View attachment 863
ARS is then set like this. (We don't use 9 for an outside call)
View attachment 864
This is how we config system by default you might want to do things different depending on customer requirements, e.g if you have a high number of users and most display the main number and just a few want to display their DID then I would do this differently with two ARS tables. One to use a set number in place of "Internal data" and the other as above. This would save the time in loading the main number in all of the users SIP tabs.
Or another option, if your carrier has the option to replace an invalid outbound caller ID with your desired number (main number) then you could set as above and just load the DID in the users that want this. All others would use the extension number which would be replaced by the carrier.
There are number if options and different ways of doing this it really depends on your preference and the carrier. What I have detailed works very well for us and it's what we use most of the time.