my friend, you are a little confused.
the TN2198 is a 2-wire ISDN U interface, your Polycom is a 4-wire S/T interface. You need an ISDN 2 to 4 wire converter to connect to your polycom (called an NT-1), same as you would if your ordered a BRI from your local Telco, which would be delivered on a 2-wire circuit.
The ISDN B1 and B2 are logical 64K data channels, they all come off the 1 2 wire circuit.
You add 2 Data modules for each BRI, you assing them to the same Port, for example, they both get assigned to 01A0501, thats how you get it working. The SPID information is sometimes needed, you will need to play around with it.
The link I posted above has the wiring diagram for the TN2198. If you wanted to do this without an NT1 2-wire to 4-wire converter (U to S/T interface), you need to buy a TN556D pack, which is a 4-wire S/T version of the TN2198
Mitch
AVAYA Certified Expert