Trying to connect with charter over coax. They have an adtran. Incoming is fine. Can not get calls out. Says something about user busy and I get a busy signal. Charter guy says it is because the system is trying to register using "officeserv". There is no username, password, registration address in the Sip Carrier options. Just the carriers IP address on the network. Had tech support log in even. Support says it's them...they say it's us. What are we missing? The MGI16 is connected through the customers switch as is the system. Should the MGI be connected directly to the adtran?