Is it possible to trade in a device I am still paying on? I plan to purchase the new Pixel phone from the Google store and bring it over to Verizon. Is it possible to trade my phone in for any sort of credit based off of what i've already paid for it without having to complete the full purchase of the phone?
If your phone is currently on a payment plan, you cannot trade it in for credits. In some cases, depending on the phone, you can give the phone to Verizon after 50% is paid off and the rest of the debt is forgiven, but you certainly don't get credits toward a new phone.
You may be able to get the balance due on the phone and then some through eBay or Swappa, or selling it privately. Then just pay off Verizon and be done, and use the rest to help with the cost of the new Pixel phone.
You can't do a regular trade in on a device you haven't paid off. the only other trade in option is an annual upgrade, which you are not doing.
Your best option is to sell the phone and use the cash to pay off the installments or reimburse yourself for the Pixel.