Product: Vehicle loan or lease

We were leasing 2 XXXX vehicles and the maturity was XX/XX/18. 
Last XX/XX/XXXX we received letters from XXXX that close to the date of the maturity of our leases we had to contact them, and we did call them only to be told that was too early and that we could visit our dealership when we were going to be ready for the purchase. 
I need to mention that we were going to purchase both of the vehicles because of extra mileage. 
So on XX/XX/18 we drove both of our cars to the XXXX XXXX dealership on XXXX XXXX ( the XXXX. XXXX location ) as one of our cars was scheduled for an oil change at their serv. dept. We asked to see the sales manager so we can talk about the purchase of both cars, he asked us if we wanted to look into a new purchase and we told him that we -couldn't- because of the extra millage on the leased cars we had. He told that we could work out a better deal if we buy 2 new cars instead of those old ones. Of course again -our biggest concern was the extra millage and the fee that we were going to have to pay- but the sales manager told  us that it was not going to be that big of amount and that we could work a payment settlement with XXXX XXXX when they'll contact us. 
One of the leased cars had some manufactures issues that we were dealing with through out the last 2 year with the same dealership and the sales manager was aware, still he persuade us that, that was the best thing to do. To return the old defected car and the other one, and get 2 brand new ones on a good deal and work out a monthly payment deal on top of our purchase payments for the extra millage fees. 
Once again, we were asking how much more it would be and why the amount could be included in the new purchase, but after consulting with the Financial Manager we were told that Hyundai wont finance us due to our credit and they looked into other financial companies ( Needless to say that they never mention to us that doing something like that meant that we had to pay a {$400.00} fee per vehicle for disposition plus excess wear and use, plus taxes on everything and on top of all we never signed anything regarding inspection for the returned cars, they never gave us paperwork regarding the returned vehicles, nothing regarding the millage and the excess wear cause there was no inspection done while we were there ) A month later we received 2 letters ( one for each returned car ) for outstanding fees as they call them. They are asking for {$16000.00} for one car and {$5400.00} for the other, when the sales manager said with certainty that it was not more that {$18000.00} for both cars. Again, he or the financial manager, never said anything about extra fees. 
When we called the XXXX XXXX dept. and asked about these fees and to arrange a settlement to pay, we were informed that such thing is not possible! That we have until the XX/XX/2018 to pay in full the amount for both cars -or- they'll send it to collections agency. I did try to explain to Ms XXXX ( the person on the phone ) that its not possible for me to pay all this amount of money in such a sort period of time and that we were told otherwise from the people in XXXX XXXX dealership on the day of return of those vehicles plus that we never received any paperwork for an inspection done on those cars and the answer was that it was MY responsibility to know what to do and that the people in the dealership could have had forgotten to mention the details. That I should had call the Lease Maturity dept. to find out how exactly i had to return the cars before going to the dealership. I asked to make a monthly payment deal, even for 12 months and she said that is not possible either. that the payment can be extended to the fullest of 120days from return which is the date she gave me XX/XX/18. She also told me that i can pay by debit card over the phone or mail a check of any amount I want but if the total amount is not paid off till that day, then the rest is going to be send to collections agency and that will ruin my credit! 
As I mentioned before, we wanted to purchase both of the vehicles and that was the reason of our visit to the dealership ( besides the oil change ) that day, but we believe that the misleading and manipulating ways of those people drove us into this rabbit hole. 
We are unable to pay in full almost {$22000.00} till the XX/XX/2018, we need to arrange a monthly payment plan so we can pay off those outstanding fees. We need more time not 4 weeks.