We entered a voucher with the wrong vendor. It was posted to our accounting system. I need to cancel that voucher and re-enter to the right vendor. What to do?

In VISCO, create a negative voucher (against the mistaken vendor), apply it to the container, post it into your accounting system and both systems will show 0 cost for the (mistaken) vendor. Then enter the actual invoice again with the correct vendor in VISCO and post to your accounting system