Phone upgrade next month, do I get a free iphone5s or do I pay a little extra?

I have an iPhone4. My upgrade is next month on O2, I pay £22 a month, I want to get an iphone5s, I don't get the world of upgrades, do I get my iPhone 5s for free or do I have to pay extra? Especially if the iPhone is the newest edition! Do I get the iPhone for free with the same data and calls limits and all that? Please could you explain some good info as I don't get the world of upgrades! I'm so confused!

When you upgrade you still have to pay for the phone.

You will have to pay for the phone itself, and whatever plan (if you want one).
You should be able to see everything on your provider's website.