Can you use the iPhone on the $50/month for at&t?

I'm planning on purchasing the iPhone 4s but I don't want a contract. I was looking at the prepaid $50/month plan, but the iPhone isn't on the prepaid phones list. I just need to know if I have to purchase an at&t contract for the iPhone.

Haven't you already answered your own question? The iPhone isn't on the prepaid phones list. Can't you read what you typed?