Walmart last week announced the availability of iPhone 5 on a Straight Talk no-contract plan with unlimited voice, text and data, but like most so-called unlimited plans, this one too has a limit. For $45 a month, you can use up to 2GB of data, which these days isn’t a whole lot. Stream a movie on your shiny new iPhone? Not likely. However, Walmart has made it easier to buy an iPhone 5 off-contract by offering $25-a-month financing on the purchase of a phone as long as you use a Walmart credit card. Only a few prepaid providers offer the newest iPhone (Cricket ; C Spire, a regional provider in the South), and you’ll pay $649 up front for the phone. At Walmart, you have the option to buy the phone outright or put it on your card with no interest fee. It’s no secret that carriers use the term “unlimited” to describe plans that indeed include what the industry calls a soft data cap.