United Debt Services Received letters that look like debt collections (pink) but not behind on my bills www.uniteddebts

 I have twice received a letter from this company ( pink letter in white envelope with the words "Department of Negotiations " showing thru upper left window) and I'm furious...I live in a small rural community and these letters look like debt collectors, and Im sure that's what our postal carriers think. I am NOT behind on my bills and have NEVER contacted this company other than to yell at them after the 1st letter, and told them to remove my name from their mailing list, but they just laughed. Is this even legal sending a letter that looks like a debt collector? I feel like they are giving me a bad name.