To reverse a Cash Receipt transaction that has been processed incorrectly you can process a negative cash receipt and then process a new transaction.
Suggest you consider doing both these transactions with a new/different reference number so they are not recorded in a normal cash receipt batch.
Even if the original cash receipt transaction has been offset against other transactions (i.e. Invoices), as long as those transactions are still on the Customers ledger you can offset them with “negative” cash receipt amount so that they show as owing again.