CompuServe Messages

Here is my situation: We have to satilite offices; one in Chicago and the other in San Fransisco; and both offices need to have access to information stored on our Novel NetWare 3.11 server. The San Fransisco office is running with NTServer, but the Chicago office has no network installed ( probably wont for sometime ). We currently use cc:Mail for most of our inter-office communications, but Lotus Notes is also used for general information sharing. We also use Microsoft Access ( V2 ) for general database stuff. Every hour ( one the half hour ) our office phones the San franscsco office and transfers all waiting cc:Mail messages; they intrun calls us every hour on the hour. The replication schedual for Notes is every 120 minutes. The Chicago office currently uses cc:Mail Mobile for Windows and call in when the feel like it. We also make a tonn of telephone calls to these offices, mayby 30 a day. As you can see, there is a lot of communications between these three offices and the phone bill is climbing. My question is this: " Would an ISDN connection to these location help'. I know that we would see a speed increase but what other benifits would we have ? What type of hardware would I need to install on my Server ? Thanks in advance, Rowan.