When I sign into My Account on Verizon.com I get a notification to sign up for Call Assistant. When I click the "click here", enter my phone #, yada yada, I get an error message that Call Assistant isn't available in my area, and to enter my email address and mobile number to be notified when it's available.
I have the same question and same symptoms reported by the OP.
Only difference is I'm a FiOS customer in Essex County, NJ.
And it's been taunting me to sign up for VCA (without actually allowing it) for a month or two now.