While you could, I suggest that you do not. There is a 99.99% change you would get a lot more by selling the phone yourself on Kijiji or FB marketplace. Trade-ins are greatly undervalued.

My understanding is that you would get charged if you use the credit to purchase a phone. Ill find out.

Certified pre-owned phones can not be purchased in store.

What you can do instead is buy the pre-owned phone in store, then go into a Koodo store and ask for the trade-in later program in which they will give you a shipping label to send off your phone. When the trade-in company receives it and verifies its condition, they will send you a credit in the form of virtual mastercard that you can use for online purchases.

If you’re an existing Koodo customer, you should be able to take the SIM card from your “trade-in” phone and insert it in your certified pre-owned phone. A new SIM card is shipped with the certified pre-owned phone which you can use as backup or swap the SIM card using your self-serve account. This should eliminate the $50 connection fee. 

Depending on the age, internal storage size and overall condition; iPhone and Samsung devices typically fetch top dollar and tend to sell the quickest on Kijiji or FB Marketplace. If selling a less popular brand, it really comes down to how much time you’re willing to spend waiting for a potential buyer. Since ad placement is free with these sites, try your ad out for a week or two. If there’s little to no interest, consider selling to a friend, coworker or a family member.