Which phone company has most affordable plan for iphone 4s?

I'm settling on getting a 16GB iPhone 4S. I don't want to spend any more than about $90/Month. I only plan on using no more than 1GB of data per month. For you iPhone users out there, I want to know the most affordable plan and how much I should expect to pay, since this is a popular phone.

This "was" by far the cheapest plan available and it includes iphones. As always, make sure they have good coverage in your area or the main areas you travel between.
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Starting on January 11, 2013 in more than 2, 000 Walmart stores and online at Walmart.com, customers now have access to the iPhone 5 and iPhone 4 on Straight Talk's $45 no contract unlimited talk, text and data plan. To make this offer even more affordable, Walmart will be offering customers who purchase the phone in the store, a no interest fixed-monthly payments special financing offer for only $25 a month with a Walmart Credit Card.