It works like this:
We've been using ting for about 3 months now and it has been wonderful. No problems with coverage, billing, etc., and the customer service is top-notch. We haven't paid more than $50/month (mostly under $40) for two phones with talk/text/data.
If this is something you are interested in, use this referral code and get $25 credit (which goes a really long way) when you sign up!