How to apply payment to correct invoice

I created 2 invoices a year apart. I received 2 payments a year apart.
Somehow the payments got applied to the wrong invoice. Don't know how it
happened, since they were a year apart. The amounts are the same so I show
a zero balance, however I want to correct the payment to the correct
payment. i.e. Invoice 1 should have been paid by payment 1, Invoice 2
should have been paid by payment 2. 1 was paid by 2 and 2 was paid by 1.
Any clue how I can straighten this out. Tx