I don't have a T Mobile phone, only a Sonic HotSpot. I don't have a 10 digit phone number, only a 9 digit account number and I can't seem to set up a My T Mobile account without that extra digit. I could use some help - can't see my bill without goint to My T Mobile.
If you open up the Sonic Web Admin page (mobile.hotspot or 192.168.1.1) while connected to the hotspot, you will notice that your phone number is displayed on the top of the page. To set-up your account, please use the telephone number referennced on the page.