The only way to guarantee that an Order is canceled/amended is to communicate directly with your vendor point of contact.

You can message with a Vendor through FusiformCAST on the web portal at clinic.fusiform.co for updates , however the Comments Messenger does not guarantee that the Vendor will see the message in time. 

When reaching out about order changes, always, always get confirmation of receipt of the message from the Vendor. The safest way to achieve this is to call or email the vendor point of contact directly.