500 Fast Cash Mislead information which the individual keep paying financiall charge and still have remaining balance of the original loan, Internet

I request a small loan through Money Mutual and 500 Fast Cash is the lender.  I was given $350.00 and the finance charges are $105.00.  I was under the impression that starting on August 24, 2012 they would withdraw $105.00 until I paid off the loan.  However, I paid $210.00 and I still own the original balance of $455.00.  I don't have a clue way will I keep paying $105.00 finance charge if my original loan was $350.00 x 30% = $105.00 finance charge. 

Instead their  wording  to rip off an individual are as followed "By receiving a loan through 500Fast Cash you agree that your loan will be renewed unless you request to pay down an additional amount toward your principal , or pay out the balance in full." They offered an example : for a $300.00 dollar loan the fee is $90.00 , and on the 5th renewal you pay $140.00 which equal $90.00 renewal fee plus the $50.00 pay down.  If you renew you loan again on the next due date, your principal balance will be $250.00 with a new renewal fee of $75.00.

when the automatic paydown process is in effect this will decrease your principal loan amount and your renewal fee) Whatever that is.  I think that these people are taking advantage of people in need of a small loan and you just keep paying and you never see where you money is truly going so far I paid $210.00 dollar I increased  $50.00 dollars on the loan to pay them off, but I still own them $455.00.  Don't know where they money is going but would like someone help. Open for advise.