Hello there, fayad.
To make sure we're on the same page, are you trying to change the invoice amount or the number? Also, may I know what is currently connected to your refund or credit note? Do you mean you want to apply a credit to your invoice? If so, what issue do you encounter?
I appreciate it if you could tell me more details about your issue. Anyway, if you have any other concerns with invoices and refunds, just let us. We'll be sure to help.