How can i upgrade my Samsung 3 for the new Samsung 4? I hear from friends that you just trade your phone in or something. I activated my Samsung 3 at future shop and they recommended Koodo. By the way i love the service i get with Koodo i recommend Kooodo to all my friends. You guys Rock!!!!!
Sell it online at Kijiji or Craigslist (watch for international scammers on Craigslist especially).
You could probably get $350-400 at the top end if it's in great condition. It's doubtful that you could get anywhere near as much from Koodo, but you are welcome to try.
However, the upgrade will still cost you a good chunk of money out of pocket. With the $700 cost, even if you got $400 for the S3 by reselling it online, that's still an additional $300 more for the upgrade minus any remaining tab you have run down that you can use. Throw in taxes of another $80-90 or so, depending again on your tab discount, there's a good chance you could have to pitch in nearly $400 for the upgrade.
You could try to buy an S4 from somewhere other than Koodo if you can find it cheaper, but be weary of where and what the warranty situation is. Still, you will have to pay a good chunk out of pocket.