Q: Can't remember $24.99 purchase please let me know what it is for. Thanks

We are fellow users here on these forums, you're not talking to iTunes Support.

$24.99 is the amount for iTunes Match in the US : http://www.apple.com/itunes/itunes-match/ - was its auto-renewal due ?

If you log into your account on your computer's iTunes via the Store > View Account menu option, you should then see a Purchase History section with a 'see all' link to the right of it. Click on that and you should then see a list of your purchases (I'm not sure if iTunes Match and/or other auto-renewing subscriptions show there).

If you can't find what it's for then you could contact iTunes Support and see if they can help : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption