Product: Debt collection

In XXXX, my husband and I moved to another city at the end of our lease. Apparently we were charged a crazy amount cleaning fees after we turned in our keys. We had no idea we even owed money to this apartment complex until XXXX when I my husband I checked our credit looking to purchase a home. Since then, I have sent NUMEROUS validation attempts directly to the credit bureaus, apartment complex itself, and then to Hunter Warfield. Even after sending them letters from our NEW address, HW has claimed that they have been sending their responses to the old apartment address, which in turn we had not received a one. Obviously we dont live there anymore, that is why you are trying to hustle money out of us. I am at my wits end and this is the only way that I can see to rectify this situation. 
In XXXX of this year, I visited the HW website directly to attempt to make a payment, I saw the option to negotiate a settlement with this account and I jumped at the opportunity since this account is the ONLY hold up for my husband and I to proceed on with a purchasing a house. I was given an offer of {$1500.00}, unfortunately I didnt have that full amount available so I pushed the pay date out to XX/XX/XXXX. ( Pics attached ) As an XXXX XXXX XXXX, I was XXXX  to XXXX during those 2 weeks and had to XXXX. Unsure of my return date to work, I had to secure our finances and I made an executive decision to not make the payment and re-negotiate a new deal at a later date. After returning to work on XX/XX/XXXX I decided that I was clear to move forward with the settlement offer. I logged into the website and was given and offer amount of {$1400.00} with a payment due by the XXXX of XXXX. I go to make a payment today ( XX/XX/XXXX ) and the site was requesting the full amount again and not allowing me to pull my original settlement offer. ( Pics attached ). I called the company to just make the settlement payment over the phone and was met with extreme rudeness and complete disregard for the truth seeing as though this company TO THIS DAY has yet to provide me with any proof that I even owe on this ridiculous account. After being told that HW doesnt even allow settlements, I had to send a snapshot of the pics provided to show that was in fact not true. Its a whole option under payment on their website. I was even hung up on today after being told Why didnt you just make the payment in XXXX when you got your first settlement offer then. To which I replied that is none of your business, I am trying to make a payment now. After they expressed that I couldnt make any partial payments online if it wasnt in an amount that HW agreed on. What kind of business is that? If I wanted to pay {$20.00} a month until this account was paid in full, that is my legal right to do so. After that conversation, I was hung up on. I feel defeated and I would just like this account removed from my husbands and my reports. This company is obviously up to some shady ways of operating and it seems that they do this with all of their customers after they harass and disrespect them. They refused to prove that I owe this account and the refused to accept ANY payment that is not in full or a monthly payment amount that they approved.