I have to change a bank account number in QB Premiere and also change the bank log in. Can I just change the account number in QB and in QB bank log-in, or is there a better way? (and how? so I keep all the "old" info"

I'm here to make sure you can change your bank account number without losing any old transactions, @IIt is Just Me!

Does this new bank account number contain all the transactions, including the old one? If it does, then we'll have to deactivate the old one from online banking, make the necessary changes, then reconnect again using the new one. 

Follow the steps below on how to disconnect your account from online banking:

1. Go to the Lists menu located at the top to get to the Chart of Accounts. 
2. Right-click the bank account that needs to be deactivated, then select Edit Account. 
3. Now go to the Bank Feeds Settings tab and select Deactivate all online services.
   
4. Click OK to confirm.
5. Click Save & Close.
   
   

Then, update your bank info from the Chart of Accounts window.

1. Right-click the bank account, then select Edit Account. 
2. In the General tab, make the necessary changes.
3. Click Save & Close.

Once done, reconnect again using the replacement credit card information. Here's how:

1. Go to the Banking menu at the top to get to the Bank Feeds and Set Up Bank Feeds for an Account.
2. In the Enter your Bank’s name field, type the name of your FI.
3. Choose which FI to add to QuickBooks in the Link your Accounts screen.

For additional resources, consider checking out this article: 

• Disconnect Bank Feeds for an account in QuickBooks Desktop
  Edit Bank Feed settings for bank or credit card accounts.
• Connect your account to Bank Feeds
  
  

Otherwise, if these accounts have separate bank statements, you have the option to add a new bank account to keep track of your transactions.

Visit me here again in the Community and keep me posted on your progress with this banking issue, I'm determined to help you succeed.