Handling Incoming GSM Calls?

I have two GSM lines in my G400P

I know that doing this:
[from-gsm]
exten => s, 1, Answer()
exten => s, n, Dial(SIP/431)

Will send all incoming calls to extension 431.
But how do I send calls from line A to extension 431 and callins from line B to extension 432?

I think you should set different context for line A and line B. For instance:
line A:
[from-gsmA]
line B:
[from-gsmB]

"Line A" and "Line B" are two seperate SIM cards in the G400P device.
They are nothing more than EXTRA/1-1 and EXTRA/3-1.

Can I define context based on that?

you should edit your extra-channels.conf, change the context of EXTRA/1-1 and EXTRA/3-1 to different

That works nicely. Thanks.