hautest, Welcome to PinStack.
Don't know about Google Talk and Cingular, but does it download and install correctly? Sometimes when Cingular says they don't support an Application, it just means that they won't be able to help with problems that occur. Other times it mean that the block the service books required to use that service/app.
If it installs, then it should be usable, if not you're likely out of luck.
Hope this helps