SIP Alias in Asterisk Call Manager

I’ve developed a PHP script that connects to the Asterisk Call Manager to setup a call using the Originate action. I am submitting the below:

Action: Originate
Channel: SIP/1910
Context: from-internal
Exten: 8135551212
Priority: 1
Callerid: 3125551212
ActionID: 3

Now, this works great. The only problem is, the source of the information for that PHP script does not give me extensions, it gives me usernames. Inside the FreePBX Administration portal, I set everyones “SIP Alias” to be this username. However, I can’t seem to specify that as the channel. I have tried all of the following:

Channel: SIP/user
Channel: user
Channel: [email protected]
Channel: [email protected]

The last two appear to almost make the call, but it still fails and says it can’t make the call.

Does anyone on here have experience with the SIP aliases and with Asterisk Call Manager that could point me in the right direction. Unfortunately, a Google search for “sip alias asterisk call manager” only seems to pull up Cisco stuff.

Appreciate the help,
Jason Greb