You can follow the steps from the following link. https://www.koodomobile.com/en/help/moving-prepaid-postpaid-monthly-service

1. Make sure you have an active Prepaid Koodo or Public Mobile account. If your prepaid account has been suspended it must be topped up before you try to switch.
2. Pick a phone or, if you’re bringing your own phone, pick a SIM card.
3. If you don’t already have a Koodo Postpaid account, when adding your phone to the cart you’ll need to select “I’m new to Koodo: Let’s get started”. Just so you know, even if you already have a Prepaid Koodo account, you’ll still need to select “I’m new to Koodo: Let’s get started,” so we can set you up for monthly billing.
4. If you received a promo code from us in either an email or SMS, you'll be able to redeem it on the "Your Order" page. Check out Redeeming your Koodo promo code to see how.
5. Next, you’ll need to pick a plan. If you want to keep the same phone number, follow the steps in Moving Your Number to Koodo.
6. You’re all done! You’ll now need to wait for your phone or SIM to arrive!

Once your number transfers, your original pre-paid account will be automatically closed. You will lose any remaining $ and booster balances, so try to use them up before making the switch. If you have to top up, switch to the cheapest prepaid plan available to tide you over.