Changazi is an ex-policeman turned businessman who helps Mortenson. Changazi means "of the family of Genghis Khan" (8.7). and although he seems sketchy at first—like when he locks Mortenson's supplies away and doesn't let him see them—he doesn't swindle Dr. Greg. Sure, he takes a little cut of all Mortenson's money for himself, but he more than compensates for it with his "vast network of contacts" (10.23). That's just the price of doing business in Pakistan.
One of Changazi's invaluable connections is Ghulam Parvi, his accountant. Not only does Parvi help Mortenson get his building supplies from storage when Changazi is out of town, he becomes an invaluable asset to Mortenson, who says, "I never would have accomplished anything in Pakistan" (12.17) without him. Mortenson ends up hiring Parvi to help full-time while he's in Pakistan.