I remember agents demanding electricity bill as proof. And I think if bill doesn't match then cnic copy of the person who's name it's on has to be given. Not really sure of the exact modalities.
+92 321 4223737
You can contact this guy for exact info. I used his services to get our company car registered and it was a smooth enough process.
+92 302 4717555 Ali
Another agent that had slightly higher rates but is also trustable, my cousin's car got registered through him.