2 movie rentals only seconds downloaded and fully charged $ - can I retrieve either movies or refund credit?

Rented 2 movies from iTunes on ipad Air using iOS 8. ? - neither downloaded properly. one for 1.13 minutes and one for 17 seconds. The rental costs subtracted from my credit but unable to view. tried to complete download which I guess was interrupted initially but to no avail. Now I have viewed the 17 seconds or 1 minute I cannot access again. Waste of iTunes credit - what can I do to correct this?