I had a brief FiOS internet account at a different address, and then I canceled it. However I lost the box that the router came in, so what is the address that I need to send back the router?
I am in Dallas TX
In theory you can take it to any UPS Store and tell them it is a Verizon return, and they will send it back for you.
Alternatively you can call Verizon and ask for a return shipping label, and they will send you one.
Call customer service and explain them that you want to return the router OR you can just return the router at a verizon retail store.