"Own" could use some unpacking here.
You don't truly own the car or the home, the lender has a lien meaning they effectively own it until you pay the lender. For these large assets, the lenders are able to pursue them more easily (repo, foreclosure).
For a phone, it just depends on the terms. You didn't pay it in full, the lender paid it and expects you to pay them back. It is up to the lender if they want to pursue the phone or the cash. Since it is difficult to pursue the phone, it is more likely it will go to collections.
Now, the question is do you "own" the phone? Sure, you maintain possession of it despite being taken to collections. But, if you want to clear that negative mark, selling the phone is the most obvious way to get the funds to pay it. Strictly speaking you own the phone, but if you look at the reality of the situation one could make the case that you truly don't or more accuratlely the true cost is greater since you decided not to pay.