Use hyperterminal, dial to these 2 AT&T numbers:
1. 1-800-543-3279, non v90 line
2. 1-888-296-3892, v90 line
Both lines are 10 cents a minute, but I doubt 20 cents will break your bank.
You should get a login screen on both numbers. Post back results. Does one connect quicker than the other, do they both take a long time to negotiate, are they quicker than your ISP? You might try a connecting a few times to each to get consistent results. The results will tell me what direction to go next.
Matt J.