Hello! Thank you for using Apple Support Community.
If you are trying to zero your balance and still have a valid credit or debit card, you may purchase an item from the App or iTunes Stores for more than your balance. The remainder will be billed to your card, leaving you with nothing in your account balance.
Alternatively, you could ask Apple Support to remove and keep the balance. Remember that the people on this forum are just other Apple products users like yourself and are unable to do this for you. Use this link Apple provides to take you directly to the managing and editing an Apple ID people who will do this for you --> https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0998&symptom_id=20198
If you choose the Apple Support option, use the direct link I provided. It might save you some time over using the general support link to Official Apple Support because the general one will just eventually take you to the direct link anyway. Using the link I provide will save you some time.
Alternatively give Apple a call:
Contact Apple for support and service - Apple Support
If you are asking about this because you are changing regions, take a look at this article:
Moved to a new country or region? - Apple Support
Have a great day!