Exorbitant interest rate

I purchased a vehicle in November 2014. At the time of entering into the agreement I noticed that my interest rate was exorbitant considering I have a very good credit scoring- Wesbank hit me with an interest rate of prime +4.25%....leaving me with an interest rate of 13.25%. Other people I have spoken to have all advised that their vehicle finance interest rates are prime +1 or 2 max! I queried my interest rate at the time but was told that it was due to the fact that I am a foreigner (born in UK but moved to RSA at the age of 1 years old so have actually lived in RSA all my life) and that it is my first car purchase. I told them I was not very happy and didn't want to go ahead but they advised that I would be able to have my interest reviewed after one year. It is now a year later and I have asked to have my rate reviewed as I have proven that I am not a risk lender and that I have a great credit scoring. The reply I received is that they are unable to amend the existing rate as it was quoted as per my credit profile!!! My credit profile is good so why am I being punished with such a high interest rate??? I would like an explanation