500 fast cash Rip off artist and harrasment Miami, Oklahoma

I received a loan from 500 fast cash not really reading the fine print. Today I finally decided to do some research to see who else they ripped off and who has been receiving threatening phone calls. As I can see their are many of us. Long story short I borrowed $200 and in interest alone I have paid $420. Once they took all that money my interest payments were suppose to go down and the principal. After they took their interest payment of $120 they turned around and took an additional $30 without my consent whiched caused and overdraft and continued to do this 3 more times. Since then I have received threatening phone calls at my job, home and cell phone. I told them I would settle for $30 for the remaining balance of $75 but they dont want to budge. I still receive the calls 3 to 4 times and daily and dont know what to do. I wish their was some type of lawsuit we could proceed with to eliminate these scammers.