Q: I want to stop a transaction from my iTunes account because the money is not available on the account and I do not want to receive an NSF on my account, so how can I stop that payment?

What sort of transaction ?

If it's an auto-renewing subscription that is due then there are instructions on this page for managing and stopping them : http://support.apple.com/kb/HT4098

If it's a pre-order that is being released then see this page : http://support.apple.com/kb/HT5714

If it's something that you've already 'paid for' then purchases are considered final, but you can try the 'report a problem' link to contact iTunes Support and see if they will cancel/refund it : http://reportaproblem.apple.com

If the 'report a problem' link doesn't work 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, then Purchases, Billing & Redemption