500 Fast Cash Loan was $350.00, made 4 payments of $105.00. Now they want $525.00 more to pay in full. Internet

  I borrowed $350.00 from 500 fast cash. They deducted $105.00 from my checking account in Jan. 2012.    Feb. 2112, for $105.00.   Mar. 2012, for $105.00,  & April for $105.00.  I was understanding that it was 4 equal payments of $105.00. Then in May they took out 2 different payments 1) of $105.00 &   the 2nd) payment of $50.00.   I then went to the bank & put a stop payment on it, cause I thought it was paid in full.  They called my wife & said I owed another $525.00. She came home & told me this information & also told me they even called my wife's girlfriend looking for me.