Product: Debt collection

I had an original medical debt of XXXX from XXXX XXXX XXXX XXXX which has their billing address set to XXXX XXXX XXXX, XXXX, KY, XXXX for services rendered of late XXXX. 
I setup a payment plan with the hospital and as soon as I received the first bill I have been paying it on-time. Now my debt stands at XXXX. 
During XX/XX/XXXX, they sent me 3 SETTLEMENT offers of which 2 offered substantial days to pay ( 2001  ) and the 3rd letter only offered 11 days to pay. 
The first letter offered 25 % reduction of my bill and mentioned that I have 2001 days to pay 75 % of remaining balance. I was of course happy to received the offer and started to plan the payment. 
Later around the middle of XXXX, I received a 2nd letter that offered the same 25 % reduction with 2001 days to pay. I treated the 2nd letter as confirmation of the settlement offer and looked forward to paying the discounted amount. 
Close to the end of XXXX, the same month I received the first letter, a 3rd letter arrived still offering the 25 % discount but now it ONLY gives me 11 Days to pay from the date of the letter, which has the same date as the first settlement offer that has the start of the month. The hospital included an apology letter stating that the first 2 letters should be ignored because it was sent in error. 
I use XXXX, and most of my funds are invested. It takes at least a week to withdraw money from it since I have to sell investments, wait for it to clear, and then be available in my XXXX  card. I do have the funds available to pay for the settlement amount, but they are invested and I know I can not make the window of payment even if I start the withdraw process when I received the third letter. 
I then reached out to the telephone number in their billing statement and spoke to NPAS ( the hospital account servicer ), to request extension of the window for me to pay the discounted settlement amount. The representative then stated that they can not do anything for me and I have to call the hospital. I promptly called the hospital and spoke to their customer representative. The hospital customer service rep also stated that they could not do anything for me either and transferred me to a patient relation number, which I then called but nobody answered. 
I tried reaching out at least 10 times to the hospital patient relations an customer service during end of XXXX and XXXX leaving voicemails and callback information so the matter can be discussed. They called back ONCE but we missed it and left a message for me to call back, I keep calling back but they never called me back again. 
So, now NPAS keeps calling me about an unsettled debt because I have not paid XXXX and XXXX because I am requesting the settlement amount to be offered again since they did not gave enough time to pay. But when I try to discuss the settlement with NPAS, they revert to their run around that I have to call the hospital which I called multiple times but never responded. NPAS is now threatening that my credit score will be impacted due to my unpaid debt. They also cancelled my payment plan and I am now required to pay the full XXXX without the settlement discount. 
All I wanted was someone that I can actually speak to about the settlement offers and get a logical reason why they can not extend the window since they even accepted in written form that they made errors on the first 2 letters. 
I have original copies of letters they sent me. Pictured copies are also attached to this complaint.