Why can't I download a song on an account I've had open for many years. I can't even contact Apple at this point. They seem to be unresponsive to their long-time customers and I don't understand why. Is there a special phone number?

What happens when you try to download it ? Does it show in Purchased as being available for redownloading ? if the rights-holder has removed it form the store, or you've moved countries since buying it, then you can't redownload it - if it doesn't show check to see if you've hidden it : Hide and unhide purchases in the iTunes Store - Apple Support

If it shows but doesn't download then what have you tried e.g. logging out and back into your account, soft-reset of the phone etc ?

If you want to contact iTunes Support : http://www.apple.com/support/itunes/contact/