NT Server and modem pools

I have 1 Comtrol rocketmodemII 4 port modem card in a customer server. Three ports are assigned to the modem pool for clients to use. The customer just added 4 more lines and I installed another RocketmodemII card with 4 ports. I would like to add these 4 ports to the origional 3 ports so that the clients have 7 lines available. Nt Server is only allowing me to put 4 ports in the pool. What am I doing wrong? How do I get all ports in a pool for use by the clients???