Cleaning up Accounts Receivable

We have a small NPO who has annual fundraisers.  Some of the donors choose to pledge their donation and pay over the course of a year.  We record those pledges as a credit to the Fundraiser revenue account and a debit to Accounts Receivable (A/R).  There have been in past years partial payments made but not to the A/R account on these pledges.  Payments were posted as a "Create a sales receipt" which resulted in a credit to the Fundraiser revenue account and a debit to Cash.  It should have been "Record payment." These postings have happened in previous years and have not been cleaned up.  I believe that our revenue account has been overstated and am wondering how to clean up the A/R account (from previous years).  Thank you