Whether you keep your LG is entirely up to you. But...you can't return the LG to Koodo to negate your tab balance.
You can keep it, put a Koodo/Telus/Public sim in it. You can grab an unlock code for a few bucks off ebay and put any sim card in it. You can lend it to a friend. You can rent it out for money. You can use it as a paperweight. You can use it for personal or commercial use (not sure how well that LG would do if used for industrial use, though). Even if you move, you can keep the phone. You can use it with a VOIP provider via wifi or data as well. You can transform it into a spy camera or even a rocket. You can put apps on it, some apps might even be able to ring certain frequencies out of the speaker that'll blow out candles.
You can sell it, you can trade it in if you're doing an upgrade, you can auction it off. You can trade it for beer or almost anything else. Heck, you could even trade that LG phone for another LG phone. If you travel internationally, you could pawn that phone off as currency, as in you could probably haggle a few hotel nights in exchange for the LG phone (assuming it's unlocked).