Can I sell my sprint 4s with out unlocking it?

It's no longer on my plan and I missed the 30 day return. Gf bought me one for my bday which was the day after getting mine. She still doesn't know I had one.

Let her have the moment. But , in doing so I put it up and forgot to return it. The bill reminded me. So I switched phones on my contract because I have no need of two iPhones. Replaced with an android, cause I've been doing android app work.

So I'd like to sell it but do I unlock it first?

I know it's usable on more carriers because I watched the setup. Pcs caught my eye. Sprint actually activates it like any unlocked phone. At least from my experience with unlocking. They turn on wifi to get the carrier, that's when I noticed a few others in the list. Yes interesting .

I know it's good for sprint and pcs prepaid, must be able to use on verizon as well. Just can't AT&T or tmobile it. Though you can unlock a AT&T 4s for tmobile prepaid.

So main question. Do I get it unlocked first by haggling sprint for the program code or let it go as is?