I need a cell phone plan for my iPhone?

I have an unlocked iPhone, but I'm not sure how long I'll be using it, so I don't want to sign a contract. I need it for calling. I don't text. I don't plan on using web, but I might. But I just need a phone for calling. I looked into a couple prepaid plans like ATT and T-Mobile, but they don't have JUST minutes and if I went with their plan, then it would be $50+ and I won't be using most of the things. Anyone know of one preferably $30 or under? Or anything in that range?

All smart phones make you pay for data so you have to pay for that and it comes with messaging also with minutes so you have to buy texting and data