Q: I rented a movie on iTunes  but  it never downloaded

If it hasn't downloaded to the Videos app then does it show in the Downloads tab in the iTunes store app on your phone for downloading ?

If not then try the 'report a problem' link from your purchase history to contact iTunes Support : log into your account on your computer's iTunes via the Store > View Account menu option and you should then see a Purchase History section with a 'see all' link to the right of it ; click on that and you should see a list of your purchases ; find that rental and use the 'Report a Problem' link and fill in details about the problem (iTunes support should reply within, I think, about 24 hours).

If the 'report a problem' link doesn't work (it's been taking some people to this site on a browser instead of showing a form in iTunes) then you can try contacting iTunes support via this page : http://www.apple.com/support/itunes/contact/- click on Contact iTunes Store Support on the right-hand side of the page.