how do i buy music without downloading itunes?

You can only buy music from the iTunes store by downloading and installing iTunes on a computer, or by using the iTunes store app on an iOS device (iPad, iPhone, iPod Touch) - you can't, for example, buy/download iTunes music via a browser.

iTunes download : http://www.apple.com/itunes/download/

Sell it to someone, then purchase music from a source other than the iTunes Store.

Then you have credit on the iTunes Store, which is useful only for iTunes. Is there a reason you don't want to use iTunes?

I suggest you contact iTunes Store Support. Start here:

https://www.apple.com/support/itunes/contact/

You can't get a refund per se. But go here:

http://www.apple.com/support/itunes/contact/

and follow the instructions to report the issue to the iTunes Store. They may be able to put the money back on the card so you can then sell it to someone else.

Regards.