hi Marie, Are you a current Koodo customer? or you want to join Koodo? You could keep your Bell number and move to Koodo. If you want to do so, don't cancel the Bell plan yet. Then you can go to a Koodo affiliated store and ask them to move for you.
Nothing with bell just visit your local Koodo kiosk and tell them you want to port your number from bell to Koodo. Once the number is ported over to Koodo it will automatically close your bell account and they will send you a final bill with any charges owing them.