Flamingo Finance Company - Car Plaza Paying Intrest and Nothing is going towards my credit! Plantation Florida

I purchased my Satern Vue through Car Plaza in Oct 2006 at there plantation office in Florida. Everything is great my car is in good condition and i have been paying on time. Now i would like to get a new car because mine is to basic and i want some power to it. I went through Car Plaza because i had bad credit and they led me to beleive that with a very little down payment ($750) i can get a car and it will go throught a finance company but i will have a high intrest rate (mine is 19%). They assured me that it will go into the credit burough. Well... it didnt. I have went to 2 different car places in NJ to get a new car and they both turned me down because its not showing in the credit burough that i even applied for a car loan with Flamingo Finance or anyone in that matter. I confronted Flamingo about this because i'm paying a 19% intrest rate on a car thats i'm not getting credit for. I got the ring around. People kept transfering me to defferent people and i had to repeat myself over and over again. So i asked an employee of flamingo about what my PERDIEM was (intreest per day). At first they didnt even know what a PERDIEM was. I told them what it ment. They told me that there is no intrest per day on any vehicle financed through them. So now i'm faced with a problem. My credit is still the same as it was last year and i have this car that is not erning any credit.
What do I do?

Krystine
Little Egg Harbor, New Jersey
U.S.A.