Hi, @WillCW.

I'm here to help provide clarification about changing your account's currency in QuickBooks. 

You'll need to have the same currency if you want to merge the existing account to the old one. To be able to change the currency, you'll have to delete and recreate the account instead.

You can follow the steps provided by my colleague @juVielL on how to deactivate the old account you've set up. Once done, create a new one using the correct currency.

That should do it. Should you need other references for future use, you may also visit our help site for information: Help articles for QuickBooks Online.

If you have other questions about your account, do let me know. I'm here to help however I can.