Don,
It could be paid off early but you are still paying the same as 3 payments from April to July. 3 x 243.65 = 730.94 so looks like no break on the interest for early pay.
With only three payments left, it is possible the only amount left on the loan was the principal. Most loans front load the interest in the payments, so the first payments are almost all interest with a little prinicpal, and the last payments are then inverse
When you send in the extra payment, you need to specify that it is against the principal, and not against a future payment.
See Retail Financing - Agricredit-dll.com
"Term debt instruments can be structured without a prepayment penalty to retire early without restriction."
You need to give them another call.... Find out if you have a prepayment clause. Or take another look at that pile of paperwork you signed (without reading? - ouch!).
So there was no real savings in interest repaid for your friend, correct? If that's the case than I'll definitely take BobG_in_VA's advice.
When my friend sent his extra payments he did not specify to them to apply the extra payment directly to the principal so they applied them as future payments with no deduction of interest. I would guess you would need to speak to a manager in the AgriCredit finance department to learn how to prepay early and get a rebate or reduction of interest they are not entitled to by prepayment. I believe that if you want to pay it off, say a year early, they would have to recalculate the remainder of the loan for a buyout figure.
As I said before they would rather you continue making monthly payments through the full term of the loan so they get the most interest.