Sonic Cash Loan review: Rip off

I took out a loan for 500 bucks, and they asked me to pay them back 2,000? Where on earth 1500 dollars they come up with for interest? And I pay them monthly for 50 dollars. Huh now they are harassing me and threaten me everyday 50 calls a day, plus they call my workplace as well and my reference. They tell me to pay off my loan otherwise they keep calling my workplace so I will lose my job. They cause me so much stress. Please ban this company. Or I myself will report to police.