You need to first determine if the owner and management company of the apartment complex are by chance licensed within the state. If so report them to TREC (Texas Real Estate Commission). TREC is required to investigate any and all complaints made about a licensed member. Second, write a letter to the collections demanding payment, halt of any futher debits, and contacting the credit agencies. Have it delivered with a signature. You can also threaten a law suite. A small claims is very cheap although depending on how much you are owed you may not receive all of the amount. Lastly, contact an attorney.