[Asterisk-Users] BRI numbers

[Altus Snyman]

Good day all
I'm new to the whole pbx thing.I've setup 2 servers with voicetronix card!
Each card's got 4 ports.Ive configured it so each port is for a different 
company,so in other words if a call comes in on port 1 it plays company 1's 
welcome message ens..I did this with context in vpb.conf
Now I'm looking into ISDN bri.
Please correct me if I'm wrong.
The BRI ISDN card I'm looking at has 2 line-ports.Now I'm not sure of the 
amount but each line can have about 20 numbers.
Now my question is how do I do the same type of config for BRI cards as for 
the vpicetronix cards
In other word,1 line,5 numbers,5 company's,5 different welcome messages
Please Let me know
Thanks
Altus