I had a similar experience, non-BES data with Cingular worked for a month and then was turned off. I called and complained a lot but got nowhere.
These posts gave me hope but I have not followed up:
http://davidpitkin.com/blog/archives...w_to_hack.html
http://forums.attwireless.com/attws/...essage.id=3558
I got a myBlueberry account in the meantime. Cingular is not winning any points with me as a new customer.
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David