How to configure additional channels for connections over the WAN miniport.

Solution:

 

1. Go to the PROPERTIES of the configured remote party in the Dial-up Network.
   
2. Now chose the point SETTINGS from ADDITIONAL DEVICES.
   
3. Activate USE ADDITIONAL DEVICES here, and use ADD to activate the second B-channel (Digi WAN MINIPORT-CHANNEL 1).
   
4. As dial-number enter the same as you have entered for the remote party before.