Credit vetting

I app**** for a contract online. I have passed the pre-qualification check. All was left was the credit vetting, which for some reason I was declined again. I app**** for a contract in March 2019 and I was declined. My credit score is quiet high and I have even managed to improve the score. I phoned Telkom to query as to why I was declined as I have done some research and I was told that I have a right to know my reason for my contract being declined. I am basically going around in circles as no one knows what to do. All I need is clarification as to why I am always failing Telkom's credit vetting, I have no issues with other service providers