How to appeal a credit report entry?

I had a pending charge of about 200$ with Verizon for not returning equipment after I closed my account with them. They never sent me a return label package. So, I called customer service multiple times and explained that I did not receive the return label, to my new address. They promised me multiple times that they were going to send it but never did even though I told them my new address repeatedly.  After about 7 calls, I was promised by customer service that they wouldn't report it to the credit agencies for non-payment. 

Now, they have reported it anyway and my credit score has gone down. So I decided that fighting a corporation is useless and I called them and made the payment anyway. 

Who can I talk to about removing this from my credit report? I am assuming Verizon would close the account but it would still remain on my report for 7 years, right? But can I appeal this and get it removed completely?