Oh Heavenly Dog (1980)

Browning is a PI with a bad cold, who's sent to investigate a case by a mysterious client. He stumbles across the body of a young woman and is stabbed to death, and when he wakes up in heaven, they tell him he's "marginal material," and they can only decide on his final destination through one last assignment: to go back and solve his own murder. As a dog. A cute fluffy little dog (Benji). Undaunted, Browning begins to investigate the case as best he can around his canine disabilities (dialing the phone presents a special challenge) to solve the murders, save the girl, and see justice done.