santander took paid vehicle Internet

If I understand this, as per you, they claim the contract is really a year longer than you say it is.  You even back this up by saying when you bought the car does not jive with when they say the loan began.  You state you are positive of your facts.  If you are so positive of your case, why are you so willing to give up the car?  As per you, you told them to pick it up.  You say you are concerned about your credit reputation.  Guess what?  You now have a REPO on your credit.  Something just doesn't jive here.  If you are so sure you are correct, why would you so easily give in by allowing them to repo the car?  You say they "held my auto loan for several years".  Does that mean the loan originally was originated by someone else and it was sold to them?  What does your contract say?  What governs this matter is what is in the contract and not what you say or what they say.  How many payments were you supposed to make and how many did you make?  Were you late on any thus generating more earned interest for them?

Since calls to them aren't working.  Send them a certified letter demanding that they send you a copy of the original contract. 

You may also want to make a copy of your contract (if you still have it) and send that to them as well.