Continuous receipt of demand letter while already cleared with my loan - Consumer Complaint for Security Bank

Already called the attention of Security Bank on the first time that I received the demand letter & told me that they will addressed my concern. However, a courier came again to our house this Oct 19 having a demand letter. My husband refused to receive the demand letter but the courier went to our neighbors instead & show the letter. Please help me on this matter, I'd like to know why I am still receiving those demand letters & why the misbehavior of the courier? This caused my family bad exposure the fact that my information are highly confidential. Kindly investigate on this matter & provide urgent actions. Thank you.