I held out and around a year and a half ago Verizon offered me a decent upgrade deal so I took it.  Of course they apply the discount monthly so it doesn’t make sense to pay off the phone early, but that’s fine.  

If your phone is that old, call them or go into a store and see if they’ll cut you a deal.  You should be a free agent with a 4 year old phone.  Find a deal for new customers at a competitor and get them to match it.  If your phone is paid off, they might do it.