Help needed urgently

Dear Sir/Madam

I own a truck that was allegedly involved in an accident with another
vehicle two years ago of which I was not aware of until now as the driver of my vehicle did not inform me as they was no damage to my vehicle and it appeared not to be his fault. The other vehicle rammed into the rear of my truck at the national toll road. The driver has since left my employment. I recently received a letter from the attorney of the owner of the other vehicle
sueing me for damages to their clients vehicle.

Please advise as I do not know what to do in this regard as it is not
my fault as the vehicle rammed into the rear and I am not insured as it is
not a requirement in South Africa to be insured.

As a first step ask for proof that it actually happened...