Thank you!  

These steps will be useful when we received the refund from the vendor,

in our case we have a debt with the Vendor, so we will reducing from the pending amount with the vendor.

If I'm right, I just need to skip the bank part, report the credit from the bill, and inform on the memo something about the credit letter from the vendor, is that correct?

Having an invoice to the vendor instead of a refund is ok, as long as we report the credit on the bill?