Why did you need to buy it through Verizon and then cancel service? You can buy it directly from Google, and then even offer 0% interest financing IIRC... and it will still work any any network, as far as I know.
In any case, if you are paying full price for the device, I think you can cancel service. I don't believe Verizon does contracts anymore, but even if they do, you can usually cancel within 30 days and just pay the prorated rate for the days you had service.