How to deactivate a verizon iphone 4?

I found a verizon iphone 4. I called verizon and tried to activate the phone on my account, but they said that the phone is already activated to another verizon account and must be deactivated by the owner before i can activate it on my account?
so how can i deactivate it? Is jailbreaking an option?
if so please tell me a step by step solution

There's nothing you can do. The phone has a unique hardware ID called an ESN (or UDID or IMEI) that lets Verizon associate it to its real owner's account. Until that owner deactivates it (by either canceling their plan or getting a new phone), the phone will remain activated.

Also, even when the owner DOES deactivate it, you probably still won't be able to activate it. That's because normally when a phone is deactivated after being lost or stolen, Verizon marks its ESN as bad, and they won't allow phones with a bad ESN to be activated.

It's not physically possible to reprogram the ESN in a phone; jailbreaking doesn't let you do it. If it were possible, you wouldn't see a lot of cheap phones being sold online listed as "bad ESN". They're cheap because they can't be activated.

The *only* possibility you have is to try to activate this phone on a network besides Verizon. But most Verizon phones, especially older ones, can't be unlocked onto other networks - plus since the Verizon iPhone 4 is CDMA, the only other network that *might* work is Sprint, but nobody has ever successfully gotten a Verizon phone working on Sprint or vice-versa, despite many people asking about that here for years.