Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
If something you paid for did not download, and you do not wish to try to download it any more, and you wish to withdraw payment for it, you may not yet have contacted the right place.
If, for instance, you were trying to download an installer for a 'Norton' or Symantec anti-virus product, you would have to contact Symantec about wanting to cancel your account.
What were you trying to download? I can give you specific advice, I think, if you let me know, as to the right way to go about cancelling the service or purchase in question.