Yes. Legally the ownership of the phone can be transferred 5 times before trademark infringement occurs. Apple sold it to Verizon, Verizon sold it to you, so it can be sold 3 more times. Once you sell it, you must send Verizon a certified letter, not email, stating the date you sold it. Once this is done, you no longer owe them anything, they must try to collect from the new owner. Realistically, this is never done because you are not required to tell them who the new owner is.