Payday Loans

I'm not sure if anyone will get this or not, but we had 2 loans out both have defaulted. Money is tight and it's causing problems, with mortgage payments and other bills. We used a company called magnum cash advance, the first payment went through and we only paid the interest which is $150, the second payment we tried to contact them to make payment arrangement's and got no response. We had to put stop payments on them for making unauthorized payment changes with out contacting us. Now they are doing it again they took out another payment with a different amount over $600. The bank is sending it back, but everytime we get paid they change the amount and sneak back into our bank account even though we have a stop payment on them. Is this legal and what can be done to stop them? Has anyone else had problems with Magnum Cash advance, I'm contemplating going to our State senator and finding a way to shut down all payday loan companies, they are just like loan sharks.