TMobile (USA) Minutes Used version 0.8
I finally got the extension to work again with the new TMobile web site. The default interval to refresh is set to 120 minutes. Please set the value using your own discretion. Nobody wants to bring down TMobile's web site.
You can download the version 0.8 here.
(save the file locally and then open it from Firefox: File->Open File...)
Note: If you have never logged in to TMobile's web site before from your browser (the firefox on the current machine), you need to login once for the extension to work.