Different outgoing routes to ZAPTEL channel number

I’m setting up my first Asterisk/FreePBX system for work, and I’m running into an issue I’m hoping someone can help me out with.

What I have is a TDM800P with six FXO (connections to the telco) ports. Four of which are for our main business lines and two are for our tech support department. I have been able to separate the lines for incoming calls by setting a Zap Channel DID in FreePBX.

How do I separate them for outgoing calls when all six show up as trunk Zap/G0? I need to allow outgoing calls when a user dials 9+number, but only on the four main business lines. I’m sure there will be a time when they will also want to use the other two lines. But for right now only the four.

Also, I’m using DAHDI if that makes a difference.

Thanks in advance,