Unlimited mobile data as part of cellular service plans has mostly become a thing of the past in the United States. AT&T was in mid-2010, but grandfathered existing iPhone and unlimited service iPad subscribers. New customers or those who wanted to change plans could pick from tiered offerings with metered overage fees. Verizon Wireless introduced its iPhone 4 model with unlimited data, but  put the kibosh on that for new customers as well. To add insult to injury, AT&T is now throttling users with grandfathered unlimited plans who fall in the 95th percentile of data transfer use each month. T-Mobile’s unlimited service, by the way, throttles back to dial-up modem speeds after you hit a monthly maximum.
Sprint Nextel is the only carrier remaining with truly unlimited plans, and even it recently added a 5 GB limit to its $30-per-month mobile hotspot feature. News.com has confirmed that for non-hotspot usage with the iPhone 4S, as it does for other phones.
Sprint’s plans with unlimited data and text messages range from $70 with 450 minutes to $100 per month for unlimited everything. Sprint doesn’t count calls to any carriers’ cell phone against minute pools, either. The proviso is that Sprint has a smaller mobile coverage footprint than Verizon Wireless, which uses compatible technology. As a result, Sprint roams customers onto Verizon’s network when out of its own service area, and roaming customers are limited to just 350 MB of usage on Verizon’s network in any month.