Castle Payday Loan Big Ripoff Watersmeet Michigan

I borrowed $600.00 from Castle Payday Loans in February.  I called today to pay them off and was told my payoff amount was $1900.00.  I was never showed what the finance charge would be but just thought it would be the usual amount for a payday loan.  That is a little ridiculous to pay $1900.00 for a $600.00 loan.  I offered to pay off this loan, but at a lower amount.  They refused.  That wanted to set it up on a 4 month or 6 month loan instead, but it still came out to $1900.00.  They are crazy and I told them so.  

I don't know what to do about this.  If you have any suggestion, please let me know.  I am on a fixed monthly income and can't pay a huge amount.  I appreciate any help you can give me.