Have an at&t iphone, want to keep the phone but switch to a cheaper plan?

I have an iphone 5 that I bought from at&t. I'm paying $127 per month for an individual plan {3gb data, unlimited talk/text}. I think this is a huge rip off & I want to cancel my plan {only had it for a little over a month} for something that is more in the $35-70 range. I will be keeping my att&t iphone 5 when I cancel my plan, so I need a new plan which will let me bring my iphone & doesn't require it to be unlocked (don't want to pay to unlock it).

I can't imagine why you're asking here instead of asking AT&T.

If you bought on contract and its not done, then you will need to pay a cancellation fee unless you want your phone to be unusuable.

If you wanted to use it with other network, you need to have it iPhone Factory Unlock.