Help Changing ESN Please!

I have a Samsung SCH-A670 which broke some time ago. My friend had the same phone, with the same service (Verizon), and got a new phone, so he let me have it. He already changed his number, so the phone he gave me can't be used to make calls. I want to switch my phone number from my phone to his.
I've heard you can do it online at verizonwireless.com for free, so I tried it. I called customer service and had the people there walk me through it, however, after entering my phone number, and the ESN of my friend's phone, and click submit, it gives me this message:

Your request failed and cannot be completed online. Please contact Customer Service at 800-922-0204 to activate your equipment.

Does anybody know why?

Please, any help would be greatly appreciated

1. Changing the ESN is ILLEGAL.
2. He has a debt on the phone you have to pay to unblock the ESN number
3. Thread Closed.