I got my phone second hand from Koodoo because my old one had been stolen and the phone they gave me doesn't work very well. It shuts down randomly, apps crash and sometimes it won't send texts. Can I exchange it for another phone? I've had it for almost a year now.
You can only exchange a phone for a different on within 15 days of purchase. You can, of course, purchase a different phone and swap it onto the account. If you choose to go this route, I would suggest the Moto G.
You may be able to use your phone as a trade in towards credits to go towards the purchase of a new phone. Visit your local Koodo kiosk and they will be able to tell you if your phone has any value. You'll probably get more selling it privately through Kijiji or something along lines. Then put that money towards the cost of your new phone.