We need to change or update the royalties in the agreement. How can we do this?

You will need to close the Gig, and then create a new Gig to generate a new agreement.

First, head to the payment tab within the Gig, and clicking the negotiate button. Enter the amount you are willing to pay - in this case $0, and the reason. Once the negotiation closes, the money will return to your Vocalizr wallet automatically, and you can create a new Gig with the employee by using 'Hire Now' on their profile.