Just a little more information to add:
T-Mobile did realize that you and many others may have Sidekicks, BlackBerrys, and other PDAs with data plans. We also realized you might or might not get the device exactly on time. So... To make this as smooth a transition as possible here's what we're doing:
When you pre-ordered your G1 during the presale, we asked you which of two data options you wanted. We'll be adding a temporary free data feature to all accounts who have existing data services to allow you to immediately use your G1 when it arrives using your existing SIM card. This will also let you swap your SIM back and forth between your Sidekick (or other device) and G1 for a couple days to be sure you've gotten what you need transferred.
Then, once that period ends (its only a few days) we'll automatically remove your Sidekick data feature and replace it with the G1 feature you selected. This will ensure you're not double charged for the data services.
Now, this is important. Once your Sidekick services are cancelled, your Sidekick is pretty much useless... at least for data services and e-mail. I'd alert everyone who has your tmail.com address that you're switching to a Gmail (or other) e-mail address because you won't be able to access the old tmail.com address. Also, you'll want to sync your Sidekick to your computer using the Intellisync program (syncs to Microsoft Outlook). You can then export those contacts and import them directly to Gmail... those contacts then sync to your G1similar to how they did with the Sidekick. There's a thread around here about this if you need help with the export/import operation.
If you're unable to sync with a computer, you'll want to manually write down your contacts now to ensure you don't lose them. Its not the greatest option, but I'm trying to be honest.
You're so beautiful;
You could be a part time model;
But you'd probably still have to keep your normal job...
