SANRAL make their problem mine

I own a Isuzu double cab and have on a few occasions received SANRAL accounts for this vehicle , today i received a new account , the problem is the vehicle in the photo is a taxi , this taxi is using my number plate , i phoned SANRAL immediately ,  their response is that i must locate one of their offices and fill in forms with regards to this problem , if they check their data base they will see my isuzu , and if they check the traffic dept data base they will see i own an isuzu not a taxi , my argument is this taxi is breaking the law , why must i fill in forms , they can do abit of investigative work surely ?