On the 16th of December a 19 year old drove into my car with my 5 year old son in the car

On the 16th of December a 19 year old drove into my car with my 5 year old son in the car. He drove so fast that he carried on driving and only afterwards did he turn around. We went to the police station together where i gave a description of the incident for the police report, which he signed. I submitted all required documents to Santam for a 3rd party claim and to have my car fixed. Four months later they ask me for any evidence or videos because what the guy is now saying is contradictory. How can the story change after 4 month? My son could have been seriously injured as he was sitting on the side the driver hit. I have had my license for almost 20 years and this guy is 19 years old? It's almost 5 months and I'm still sitting with a damaged car. They clearly have no idea on the legal aspect of things as a signed police report is signed under oath now the driver is telling a different story. Pathetic