Responsible for a sub accounts bill?

[MG6391]

Someone had a "sub account". They asked me to cancel it, knowing they would get stuck with the remainder of what's due on the phone.
At first I talked to a live chat Verizon agent and they said I would have to pay for it.. 

Then I called and the person over the phone assured me that it would not be my responsibility.  So I canceled it, and now this person wants me to reactivate the line and have her take control of it. 

I tried to do that months ago but Verizon said I couldn't. I've been receiving so much conflicting information. 

I checked my bill for next month and i wasn't being charged for the phone.

Now this person is blackmailing me, and saying they won't pay for the rest of the phone and I'll be responsible for it.

So how true is this?