How much does the iphone 5 cost per month?

I have a pantech phone through at&t and every few years you can upgrade to a different phone for free. Well now I can upgrade and the iphone 5 is an option.

How much does and iphone 5 most per month with everything on it. Unlimited everything plus internet and whatever else there is haha. I don't know anything about what is on a iphone so I just want everthing.

Thanks

AT&T does not offer unlimited data anymore, and has not since January 2011. The cost would depend on the number of lines involved and other selected features.