Contract declined despite good credit history

I app**** for a R299 p.m. mobile contract with Telkom. I have not been a Telkom customer before but I have an extensive credit history in South Africa - mobile and data contracts, credit card, etc. I've never missed a payment, I have a permanent job, I have no debt, and this amount was well within my budget. I've never had any application for credit or a contract declined before. I submitted the documentation in store and was told they would call me in 48 hours. After three days I had heard nothing so I went back to the store. They told me my application had been declined. Shocked, I asked for more details and they gave me a reference number and a number to call for their vetting department. I called, and they told me my credit score was too low. Now I seem to have no further recourse which is very disappointing. As a professional statistician I am mystified as to what kind of algorithm they are using to determine my credit score, and it makes me question the competency of their credit risk analysts. I would appreciate if the company could contact me ASAP if they don't want to lose out on a valuable and reliable customer.