I can only tell you what I did. I am assuming that you gave them a post dated check. I had paid them around 2200 dollars in fees on a 1500 dollar loan. Here's what I did;
1. Stopped payment on the check.
2. Waited for thier call. They only called once and I told them I couldn't pay anymore. They didn't call anymore.
3. Allied Asset Managment started calling about 15-20 times a day. I told them to send me a verification of the debt and they never did.
4. I sent a C&D letter to them and called The Cash Store and ended up making 1 more fee payment to them of 150 dollars to have my account marked Paid In Full.
This may not work for everyone, but it worked for me. Allied Asset still calls once a day but I ususally ignore it. Sometimes, I will you a fake voice just to mess with them. Lots of fun! They're stupid and try to threaten me but I know the laws as I used to work for the DA here.