Can I trade my iPhone 4 for the iPhone5?

I have the iPhone 4 I have had it for nearly 2 years. I was wondering if I can trade my phone in for the iPhone 5 and pay the difference? If so where would the best places to go to do this?

Most of the shops will buy extremely cheap due to the fact 4s and 5 is out now, so if you want to sell it better find someone (person ) to sell it, by selling to person and not to a shop you get a better price.