How to get an early upgrade on my t-mobile contact?

I have a two year contract with t-mobile and i have six months left for my contract to end. I pay 45 pounds a month for an iphone 4. I really want an iphone 5 like now. Do i have to pay the rest of the money to get an upgrade or i have to top more money to get the iphone 5. And the iphone 5 is like 36 pounds a month. Would i get it or i'ld get the 4s

1. Visit your local cellular retailer. You can find the nearest retailer by searching online via your cellular provider's website and using the store-locator. Or you may dial *611 on your cell phone to be connected to customer service and you can ask them to find the nearest retailer.
2. Ask the customer service representative when you will be eligible for an upgrade. Usually the upgrade is available four months prior to the end of your contract, according to ATandT Wireless.
3. Ask if there's an option to pay a small fee and receive the upgrade early. Most cellular companies will allow you to pay a fee, usually between $50 and $100, to receive an early upgrade. For example, there may be a Blackberry regularly priced for $200, but you may be able to pay the fee of $50 or $75 to get an early upgrade, making the cost of the Blackberry "free." Therefore, the total cost of the phone goes from $200 down to the price of an early upgrade, saving you a lot of money.