One Main Financial Citi Financial Interest out of hand Waynesboro,PA Nationwide

 I took a loan out from (then) Citi Financial (now called One Main Financial) in 2006 for $10,000 for a sewer tap on fee and water well drilling for my new home that i was building. I just called today (May 13, 2014) to find out how the loan was doing. After paying $400 a month for all these years my loan payoff is $12,000! I asked why it was that much and the person on the phone said that its because my loan is intrest heavy and that is the amount with the intrest included for the future of the loan. I asked what it was without the interest and he told me that that was the only payoff amount allowed. I said so it should be payed off in 2 more years then adn he said "No, because you still get charged 25% interest every month on the loan as well"

At this rate I will never have this loan paid off! This is unfair and has to be illegal.