Can you buy Free Verizon Wireless Cells from Best Buy or Wal-Mart?
If any of your lines are eligible for an upgrade, you can get a free or discounted phone from any Verizon authorized dealer and active it (or one of your other phones) to the unused line with a new 2 year contract. If none of your lines are eligible for an upgrade, you will have to pay full price for a phone or find a used Verizon branded phone online.