well you have to inform them how you have the money to settle it then, no other way. Just need to convince them your money is legal and you did not cheat them by declaring less income and pay lesser tax.
I have done some readings previously as i was tempted to settle my car loan early as well.
You will get rebate when you settle your car early, but the during the first few years of your car loan, the majority of your installment goes to your interest and small portion goes to your principle. After a few years unto your loan, the lender would have recoup most of the interests, therefore to consumer, there is not much difference when we settle our car with a couple of years of loan left.

You can try use this site to calculate. Not sure if it is 100% accurate. Best way is to call up your bank and ask them to provide the settlement amount of your car loan.

Rule of 78 shows you have paid at least 48% of the 7 year total interest.

Yes its charged but interest it's not equally divided into 7 years.

Interest portion is higher at the beginning.

According to bro rapple, you have paid 48% of your interest.
So you can do a calculation if you pay off earlier and save the 52% interest is better or instead of paying off the loan, use your cash pile generate more income to offset the 52% interest and earn more in the processs.

Edit to your last post: it is 3% pa but since it is calculated upfront, the effective interest rate is much more than that.

Yes bro. Must settle 1 shot early settlement else no point ..