Yup, you can. YOu just need to purchase a PREPAID microsim - $20.
Go to a KOODO SHOP (kiosk) and get them to put in a microsim from their demo phones to make sure the iphone works with KOODO.
Then once you have bought your prepaid sim card, go to activateprepaid.koodomobile.com to create your koodo prepaid self serve account. Follow the steps and make sure to hit FINISH!!
You will receive $20 credits when you activate, so you can choose the $15 base plan if youd like. If you need any Canada-Wide talk boosters or Data boosters you can purchase extra to up vouchers while you get the SIM card. You will need the talk booster to make or receive any calls if you have the $15 texting plan.
or you can buy them with a credit card when you activate your phone online.