Most 'unlimited' data plans aren't. T-Mobile gives you 5 GB before the overage charges and pocketbook pain kick in. At least, that's the way things work now. Fierce Wireless reports that T-Mo is in the midst of changing everything about the way they do overages.
From now on, data with the unlimited plan will be truly unlimited-with a catch! If you use the 5 GB monthly webConnect mobile plan, and exceed your 5 GB monthly limit, you will see your bandwidth throttled down. No additional charges will apply, and T-Mo has even agreed to half the overage charges on their 200 MB plan.
Additionally, in 5 GB plan will now cost $40/month, while the 200 MB plan will cost 20/month.