Short story: I have no idea where I should go to report phishing scams specifically involving Verizon.
An hour ago I got a call (I have AT&T wireless service, not Verizon) telling me about "free $36 if you just enter your account information at this website", the website being verizon36.com
Thankfully, I know how phishing scams work, have the Web of Trust addon, and the NoScript addon, so I was pretty safe, but the call was from (800) 922-0204 - a number associated with Verizon - so the number was spoofed.
So, why would I want to bring this to Verizon's attention? I would assume they would have motivation to deal with the maliciously used possession of the domain "verizon36.com". (It was just registered yesterday, by the way, by someone in Santo Domingo. The whois: http://whois.domaintools.com/verizon36.com) If someone were to take the domain veriz0n.com, verizzon.com, verizonvireless.com, and start running phishing scams using the impersonating domain, I would assume they would be interested to know as well.
Essentially, I scoured the site for some place to report phishing scams targeting Verizon customers, and came up empty.