I want to add a payment and QB wants to change ther previous payment?

Hi there, @mpapay2. I've got you covered in managing payments in QuickBooks Online (QBO).

To ensure that we're on the same page in providing the resolution for your concern, are you referring to changing the payment account selected when paying your bills? If so, we can simply amend the transaction created to change it from credit card to checking. Here's how:

1. Go to the Expenses menu and select Bills.
2. Head to the Paid tab to see paid transactions.
3. Locate the bill associated with the payment, and tap Show Payments. Hit the View Details to view the bill payment transaction.
4. In the Bank/Credit account section, change it to your checking account.
5. After that, tap the Save and Close button. Then, Yes to confirm.

Moreover, if you're using online bill pay to process your payments seamlessly, we can void it and re-create it with the correct payment account. To do that, please follow the guidelines from Steps 1 to 3 above. Then, select Cancel this payment. Additionally, I recommend you inform your vendor about voiding the check and schedule a new payment directly to them using the Bill Pay service.

Furthermore, you can get a report on all money paid to a vendor for the year and apply appropriate customization to display important data: Run a report with vendor totals. 

I'll keep this thread open for additional questions you may have about managing vendor transactions. I'll be right back to answer them. Stay safe!