Verizon Fios charging me for returned equipment kit.?

Recently got a bill for $1,050 for unreturned equipment after I cancelled and paid my verizon fios after two years. Lately my monthly bill was skyrocketting from hidden fees, so I cancelled and was told I had to return their equipment via ups. I asked if I can return to the closest verizon store they said no. So I get a return kit from them 7 days after canceling and I ship my equipment a few days later due to holidays. Now I am billed for it? How can I fight it? Will calling with no evidence of confirmation get me anywhere with this company. Thanks.