Allow me to provide a couple of scenarios, and guide you on how to proceed when you undergo a bank transition.
Just to clarify, are you switching to a different bank? If so, you'll need to create a bank account in your Chart of Accounts.
In some instance, if you're bank was bought or changed its name and/or website, we'll need to disconnect it from QuickBooks Online (QBO). This only applies if you're using the Online Banking feature in QBO.
To get started, please follow these steps on how to disconnect your bank with QuickBooks Online.
Then, you'll need to connect your QBO account with the new bank's website. Please refer to this article on how to connect a bank: How to Connect Bank Accounts and Manage Imported Transactions.
Also, here's an article that you might find helpful in the future: Matching Bank Transaction.
If you need anything else, or you're referring to something else, don't hesitate to post a comment below. I'm always here to help!