CAN I DEACTIVATE MY IPHONE 4 SPRINT WITHOUT ACCONUT AND PIN #?

I bought a iphone 4 sprint from craigslist about 4-7 months ago and didn't use it until know and noticed i can call and the phone is still activated. I do not have the craigslist sellers phone number. I only know the phone number. The plan is with a 2 year contract as i see on sprint.com. I signed up with the phone number and need the account and pin number to close acconut. I want to resell but can't with it activated.

You can't.

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