There may be one other person that is using t-zones for net access. Check your account online. T-mobile seems to have opted in everyone without a data plan to pay per megabyte plan without your consent. There may be some fine print in you last bill or maybe a text message, but either way if you had no data plan there may be a surprise of up to $50 on your bill. If you do have tzones you need to call customer service and remove the pay per megabyte service and change it to no data. Once that happen tzones should work again. It will take a few levels of customer service to get credited back the unauthorized data charge, just be polite and plug away. If you try to make the changes to your plan through t-mobile's website it may trigger a 2 year contract, so call customer service first.
More info here http://www.howardforums.com/showthread.php/1740503-Lines-automatically-placed-on-quot-Pay-Per-Megabyte-quot-data-plan