Is there a way to change between two amounts of the same currency in your account balance?

No. You can split a payment between a credit card and currency in your Microsoft account balance, but not between two cards.

Hi, usually the promotional balance is some money that Xbox sends sometimes for free
But it seems that’s not your case.

In this situation the best option is reach Microsoft support via chat or callback
In that way they can see what’s going on with your balance / why do you have two separate amount of money with the same currency

Hi,

Xbox 360 content can't be purchased on the Xbox One Store or the Xbox website with your account balance. The only way to buy 360 content with an account balance is via actual 360 console. You'll need a debit or credit card otherwise. This is a negative effect
caused when Microsoft switched from a points system to a currency one.

Yes, I know from a customer point of view it makes little sense, but the issue is a software one between the generations.

Unfortunately without a 360 console, you'll need a debit or credit card. If you do have a 360 or a friend who has one, use that to pay with your account balance. As long as you use the same account that you use on your Xbox One, the content will transition
between the two.

Same way you use any other balance on the account, you need to use it on the region of the balance currency

When you say you changed your local do you mean you did a region change? Because the amount is in New Zealand currency you may not be able to see it if your account is not set up to that region. You can check your account balances and if it was added at
https://commerce.microsoft.com