It maybe that your loan company did that sneaky trick (that too many of them do - and should in my opinion be illegal) of calculating the entire amount of interest over the full period of the loan and then loading it all on the front end of the loan. So for the first chunk of the loan you end up paying the interest.
If you then want to complete the loan early you end up paying interest on the whole loan and not just the time when you had their money.
Ethically you should only have to pay interest on the capital remaining of your loan - but then who ever accused loan companies of being ethical???
Yorkshire Lad