You might want to check if your current phone is a good frequency match for the countries you are visiting. Koodo runs on 850/1900 3G, but many modern GSM phones will also cover the 900/1800 bands common in South America as well. If your current phone is a not a good match, there are many International Quad Band GSM phones available on Amazon, and you will save the unlock fee.
If you are going to use your current phone, get it unlocked while you are still monthly. You will also need a pre-paid SIM, for use in Canada available at kiosque or on eBay.ca. Will cost $20, but that's credited to your account when you activate on-line. Your number can be
ported to prepaid, and you will receive a final monthly bill for your
tab balance + unlock charge, less any unused portion of the current
month's service (pro-rata).
You will definitely need a local sim and plan when in South America: there is no roaming on pre-paid.