Hi, Jack, thanks for the advice...
The management group already submitted the case to a collection agent, and that's why I received the mail.
Yes, I still kept those letters I submitted to the manager and complained about the smoke smell while I was still there. However, I have to say that manager is a jerk, refused to signed off my letters, and wouldn't let me talk to his supervisor. So... this time, I decided to bypass him and his supervisor...
Two of my co-workers helped me write a letter to two CEOs of the property management group, and clearly stated the reason why I broke my lease and vacated the apartment. Of course, I also included the facts that the manager was unwilling to deal with the apartment rule/policy violation with the neighbors below to solve the problem, and my neighbors accused me of harassing them, and threatened to sue me... upon my neighbors occupancy of the apartment, I was unable to be asleep at night, and resulted in my health deterioration...etc.
I sent a copy of the letter to the collection agent, and stated that I feel I am NOT responsible for the charges incurred. (They asked me to reply within 30 days, and notified them that I dispute the validity of the debt. Otherwise, they are going to submit to a credit reporting agency that I fail to fulfill the terms... Well, of course I dispute the debt...) I also sent a copy of the letter to both CEOs with certified mails this afternoon.
_________________________
人生無常...