Harassment Collection letters

Incident since 2011- 2012, now 2020. First and foremost; Windstream offered me bad services first-hand. I never had the chance to use their service. I reported it to them that their service don't work in the rural area. They had a black male technician to come out collect their equipment, just as I asked and being frustrated then. And now since 2012 their collection Agency is sending me harassment letters to collect over $600, but for what? I never used their bad service and I gave their equipment to their black male technician. Windstream is money hungry due to a law suit that was already filed against them, and their losses.