Product: Vehicle loan or lease

I purchased a XXXX XXXX XXXX XXXX in XX/XX/XXXX. Payments were due monthly on the XXXX of each month according to my purchase documents. I took a home equity loan in XX/XX/XXXX and paid the car loan in full. The issue is when they reported paid in full to the credit bureaus, Santander also reported it as 30 days late. 
FACTS : XX/XX/XXXX - Car Payment Due XX/XX/XXXX, I received a call from Santander asking about my payment. I told them I was in the process of closing my home equity loan and the account would be paid in full. I also asked for a payoff letter to provide to the credit union. A payoff statement was sent via email that day for an amount good through XX/XX/XXXX. It is attached. 
XX/XX/XXXX ( Friday ) - XXXX XXXX XXXX closed and funds were available to pay car loan in full. The XXXX XXXX called Santander to see if they could send the money electronically and the credit union was told no, they had to mail a check. The Credit Union sent a check via XXXX  XXXX. Tracking number XXXX XXXX XXXX. A copy of the label is attached as well as a copy of the check. XXXX  XXXX Tracking shows the check was delivered Monday, XX/XX/XXXX. 

I am now trying to get a new mortgage and the late payment has severely negatively impacted my credit score. 

I called Santander on XX/XX/XXXX, to request copies of my statements to try to resolve this matter. I never received them, so I called back on XX/XX/XXXX. This time I told the agent what the problem was, and that the payment was not more than 30 days late and was reported incorrectly. He told me the payment posted on the XXXX of XXXX which made it late. I told him I had the tracking information, and it was delivered on the XXXX. He told me I have to allow processing time. I told him they had to post it the day they got it because it was received before the cut-off time. He said no they don't, I should have asked for a change in the due date. That was never offered to me when the agent called me XX/XX/XXXX. I asked why an electronic payment couldn't be made. He said they don't accept them for payoffs. I asked to speak to a supervisor, and I was transferred. I explained to the Supervisor the same thing and his response was the payment was late. I asked if they would delete the late payment as a good will. He told me no. I asked for copies of the statements to be emailed to me. 

On XX/XX/XXXX, I received an email with a screen print out from Santander. It is attached. What is interesting is that screen showed the payment posted on XX/XX/XXXX. This is a direct contradiction to what the agent told me on the phone. I sent a reply thanking them for the information but again requested copies of the actual Statements. I received them on XX/XX/XXXX. They are attached. 

I feel this is being done out of retaliation because they only got 5 months of interest instead of 72 months as that is what the term was on the purchase documents. I am also attaching the retail installment sales Contract. 

Issues : Why did they not accept the electronic payment when that is an option they have listed on the back of the statement? I made all my other payments electronically. 

The check was received by Santander XX/XX/XXXX ( Monday ) at XXXX. If they demanded payment was made by mail, I should not be penalized for it being a weekend. 

Payment due XX/XX/XXXX, was not made until the vehicle was paid off. Payoff check was received XX/XX/XXXX. If they would have accepted electronic payment, we wouldn't even have this issue. I was not more than 30 days late and would like this late payment removed from my credit report. 

Thank You XXXX XXXX