Product: Debt collection

When we left XXXX XXXX XXXX XXXX XXXX we vacated the property in XXXX, first notice for collection was dated XXXX/XXXX/XXXX Received on XXXX/XXXX/XXXX at that time we had not even been out of the apartment for one month. The collection amount was for XXXX which was the sum total of all the remaining months on the lease. Under Tennessee state law Tenn. Code XXXX XXXX XXXX as long as we sent a letter to the apartment complex asking that they mitigate our losses and re-rent the apartment as soon as possible then we are only responsible for the amount of rent that was not collected prior to a new tenant moving in. The apartment was rented within two weeks of the time we turned the keys in. 
Despite several attempts to get an itemized list from the apartment complex which Hunter Warfield claims to represent for the charges we are supposed to owe, no list has been forthcoming. 
So that the apartment complex could find a new Tennent ( which they did within the two weeks of the time we turned in the keys ). XXXX XXXX cleaned the apartment and left it in a much neater/cleaner state than it was initially rented at. Cleaning/degreasing all cabinets in the kitchen, cleaning all vents, shampooing the carpets and repainting any areas that needed it. We purchased the paint color from XXXX XXXX that we were told to use by the apartment complex management. Ensuring that no damage was done to the apartment and any normal ware and tare items, IE. Picture holes were patched and painted. 
Additionally, we made an earnest effort to find someone to take over our lease and when that failed we gave proper notice were current on our rent when we vacated and turned in all keys. Moreover, we sent a letter to the manager of the apartment complex asking for an itemized statement of charges and that they re-rent the apartment as soon as possible so that we may mitigate our losses which we were entitled to do under Tennessee state law. As the apartment was rented within the first two weeks the amount that Hunter Warfield is pursuing us for is null, in addition they broke the law when they did not validate the debt, then began collection procedures after they had been asked for proof of the debt and to cease collection efforts until we had proof. 
The first attempt was XXXX XXXX, XXXX we received a notice of collections for a debt that was not legitimate from Hunter Warfield on XXXX XXXX XXXX we disputed the debt, I sent them a letter stating that the debt was not ours, they sent me a letter stating that they would cease collection attempts on the debt until they could produce the statement and documentation that they had legal ownership of the debt and that it was mine. In XXXX, my wife discovered that they had parked the debt on her and disputed it with the credit bureaus, in XXXX they again started trying to collect the debt that is not ours against both of us. We have asked for documentation, proof of legal ownership of the debt, disputed the debt and asked for removal from our credit reports. To date they temporarily work with us then will quietly attach the debt and begin trying to collect on it again after a few months. We have been subject to collection calls and we still have yet to receive any documentation that was requested. The account # is XXXX. My Name is XXXX XXXX XXXX XXXX My wife is XXXX XXXX XXXX