changing data services. please help

i have the sidekick data plan and im ordering the G1.. the G1 requires its own data plan and deletes the sidekicks but as i wait for it to come in the mail will my sidekick be charged for not having that data plan anymore or does the plan change the next billing period?

Time to call T-Mobile CS or Tech Support and ask that very question.

If it were me, I would not make any changes to you current plan until the phone showed up.