iPhone & plans help.

Hey guys. As you can see by the title, I'm interested in the iPhone. My current contract with Tmobile is up in a few days, and I'm thinking of switching to a different company. I'm wanting to get an iPhone, but I'm not sure which plan to pick. This of course is an individual plan. I'm wanting to have unlimited texting, and possibly unlimited calling. I've seen that the data plan is required, but I'm not going to be using too much of that other than Facebooking. I'm just wondering, how much is the typical iPhone plan and where should I go to get one? If you have an iPhone, it would sure help. I want to know the cheapest plan offering what I've listed.