Incoming line ID

I have successfully setup my asterisk server for our office, but we have 2 different companies we answer for. I am wondering if I can add somthing before the caller ID so we know which zap line it is coming in on?



If i could just add a couple of numbers or letters before the caller id to indicate the incoming line ID.

Any help would be great!

Don no about adding to caller id but a thought might be to use a different ring for one of the lines