UNITED CASH LOANS fast cash I placed my payoff date on intial documents. They charged me extention fees instead Goodyear, Arizona

In March 2009 I made a loan online from United cash loans for $300. I requested the loan to be paid in full on May 1, 2009. On September first I noticed that there were still deductions being made from my bank account.  I contacted United Cash Loan and explained they withdrew a total of $450 so far and that the loan was taken out in March.  I explained that the amount was for $300 and well paid off.  The representative went on to explain that they sent me an email explaining that if I decline extention of loan payments and still wanted to pay it off in full, I would have to respond in writing.  One, I never received that email. Two, why would I have to have it in writing in the email when I already had it in original documents.  He went on to explain that all those withdrawls were extentions and not applied to principal loan.  So now I'm told I have to pay $350 to pay off balance after already paying $450. In total I will have allmost paid three times the original amount.