Verizon is back with its offer of a free season of NFL Sunday Ticket–and just like last year, there are plenty of ifs, ands, and buts. The deal serves up free NFL Sunday Ticket access for both new and existing Verizon customers. Unsurprisingly, you’ll need to sign up for certain service packages or upgrade your existing service to snag the discount. New mobile customers will need to pony up for a new phone (and only a few specific models); plus, a Verizon Unlimited Plus or Ultimate plan, while existing Verizon mobile users must upgrade their device to an eligible model on Unlimited Plus or Ult…