Car Rental Company Tried To Scam Me Years Ago, And Now Are Sending Me To Collections.

Location: Virginia and Florida

So back story: I live in Virginia, but my husband and I rented a car from Sixt four years ago in Miami for one day. Because of some very strict timelines at the hotel that we were staying at, it got towed at like 6 a.m. We went to the tow yard, and they told us that the rental company needs to pick it up, not us, but they gave us the keys. So we returned the keys to Sixt, that day, the day it was due. I have Uber receipts showing that we visited their office that day to return it. Months later, they sent me a bill for 12 days in the tow yard totalling over $1,000. I told them I would pay the fee for towing, the admin fee, and the loss of use fee, because that's our fault, but I'm not gonna pay an extra $600 because they didn't pick up the car for 12 days. This went back and forth for months, and then all of a sudden, like six months later, they told me that I never returned the keys at all and they were charging me for that. I demanded to speak to someone in management numerous times, but was never connected with one. Just went in circles with their claims department for literally over a year. Like from March 2022 to June 2023, this was an issue. It became a huge source of stress to receive threatening emails for so long. I got my bank involved, and my bank sided with me. I finally threatened Sixt to stop contacting me, stop harassing me, or I will pursue legal action. They finally stopped.

Fast forward to 2026. In February, I got a call from a debt collector saying they were attempting to collect a debt to Sixt. Horrified, I immediately placed it under dispute and they said I would receive a written notice in the mail. I never received one and sort of assumed they were batch contacting open claims. As I began to feel peace again, I got another call today 3 weeks later. Again a debt collector attempting to collect a debt to Sixt.

Idk what to do anymore. I read somewhere I could write a cease and desist letter or something, especially since they were required by law to send me a notice by mail and never did but just keep calling me. I'm scared this will show up on my credit report, and I'm emotionally tired of the harassment. What are my options here? Do I just send them all the old files from this case years back and hope for the best? Can an attorney tell them to leave me the hell alone or is that unrealistic?