When I was renting a house, I received loads of letters from debt collectors for the previous tenants, which all ranged from "You owe." to "You better pay." to "We're taking you to court." to "How about one third off?" to "Okay, we're taking you to court." to "Okay, how about just paying half." to finally "I really don't understand why you have not contacted us."
I have had a few dealings with them myself, parking fines and water bills among them. Anyone else?
