I'm not sure non Comcast customers will qualify for the gift card.
From the Details and Restrictions link:
Prepaid Card Offer: Prepaid Card mailed to Comcast account holder within 6 weeks of service activation and funds expire in 90 days. Card issued by Citibank, N.A. pursuant to a license from Visa? U.S.A Inc. and managed by Citi Prepaid Services. Cards will not have cash access and can be used everywhere Visa? debit cards are accepted.
From the FAQ:
Who is eligible for Comcast?s special offer on Verizon Wireless?
The offer is limited to Comcast residential TV, Internet or Voice customers. Requires new Verizon Wireless tablet activation or new two-year activation of a new Verizon Wireless smartphone by calling Comcast. Both new and existing Verizon Wireless customers are eligible.