Who Do I Contact? Collections notice added to my credit score on Jan 27th 2023 from 2019 but don't know what it is

Hi, does anyone know what 10 Verizon is? I check my credit report monthly and was shocked to see that my score dropped 69 points! I clicked to see what is going on and there was a collection report added to my account from "10 Verizon". It was added to my credit report on January 27th 2023 and says that it was opened on March 26th 2019, I haven't received a phone call, letter or any sort of notification regarding this and only saw it when I did my monthly credit score check

It is for $802!!!!!!

I have been a Verizon wireless customer for almost 20 years and do not have anything outstanding on my account. I had Verizon Fios at my old apartment, but when we moved in 2017 we cancelled the service, paid our last bill and returned the router, modem, cable box and remote. I called a few months later as well to confirm that we were paid in full and we were (did this because we had an outstanding national grid bill that I didn't know about so did my due diligence and went through all of our utility vendors). 

I don't know who to contact to find out what this is. It has to be a mistake but don't know who to speak to. Does anyone have any advice on if this is real and if so, who should I contact?