How in the heck do i record a (partial) refund???

How in the heck do i record a (partial) refund???

I have a client.
wrote an invoice for 3 services totalling $520.
He paid it online (we use zoho to authorize.net)
We went out and couldn't do one of the services

I didn't see a way to initiate a refund through zoho books, so i did a $250 refund through authorize.net.
Tried to edit the payment on zoho books, but it won't let me b/c "this payment was made on line"
When i try to edit the invoice i get a popup about it no longer matching the payment.

What do I do???

And why is it so hard to do something as common as record a refund in an accounting software???

(I'm on the help chat, but the help person isn't very helpful)