Product: Vehicle loan or lease

I leased a XXXX XXXX XXXX from XXXX XXXX Honda with the early termination of my XXXX XXXX XXXX lease, and milage overage payment included in the new lease payment. The XXXX XXXX Honda Sales Manager, XXXX XXXX himself drew up the early lease termination and milage overage and assigned it to a sales person, XXXX to process with me. Everything was processed so fast that I drove off the lot with a new XXXX leased XXXX XXXX and they kept my XXXX XXXX XXXX. 
Everything was fine but months later Honda Financial Services started contacting us. XXXX XXXX, XXXX and myself, were on a three way conversation with Honda Financial Services to get things resolved. It was finally solved as Honda Financial Services found the {$1600.00} sent then from XXXX XXXX XXXX to finalize the XXXX XXXX Lease. The monies were in some kind of suspended account because Honda Financial Services were not instructed in how to apply the monies. 
Months passed and again Honda Financial Services contacts us now through a collection agency saying we owe it another {$1000.00} on top of the {$1600.00}. 
We contact the dealership only to discover both the Sales Manager nor the salesperson no longer work there. They were not even employed there a year. 
Now I contact the Financial Manager and ask him to return my call ASAP it is urgent. I never receive any contact from him. 
So, I contact the General Manager and have corresponded with him through over 30 emails and phone conversations. He finally discovers they thought our lease was for 12,000 miles per year not per our lease agreement of 10,000 miles per year. All this information was given to XXXX XXXX Hondas Sales Manager and sales person at the time of out early termination as was the contact information to the original dealership we leased the XXXX XXXX XXXX from, XXXX of XXXX, XXXX, CT. 
We were given a new lease contract with the unpaid remaining XXXX Honda lease payment and the milage overage figures into the price of the XXXX XXXX XXXX lease.  We hid nothing from the Sales Manager not XXXX XXXX Honda. 
Now the General Manager refuses to be responsible for their calculating error and is trying to make us pay for XXXX XXXX Hondas error in calculating our new XXXX lease payments and the XXXX payoff. 
He told us that in TX the leases are for 12,000 not 10,000 miles per year, and he believes they assumed our lease was for 12,000 miles per year not 10,000 miles per year. I told him we informed his Sales Manager, Salesman, and Financial Manager that our lease was for 10,000 per year at {$0.00} per mile over. We did not hide any information or contact information. Plus XXXX XXXX Honda had access to our records through Honda Leasing. Nothing was hidden. 
We are not responsible for XXXX XXXX Hondas miscalculations, failing to collect proper data, and failing to have proper procedures in place as a check and balance for their transactions. 
We are consumers not seasoned car dealers.

I told the Sales Manager I could only spent a specific amount per month on a leased vehicle. That does not mean lease me a vehicle for the specific amount I can spend on a lease per month and then claim you miscalculated data and months later send me to a collection agency to collect the remainder of the money XXXX XXXX Honda wanted for the XXXX XXXX XXXX lease.

Remedies are that they pay their error directly to Honda Financial Services and contact the credit bureaus to have this collection cleared from my good credit.