If you are using the Sandbox and testing the Braintree credit card integration you might want to look at their documentation for testing credit cards.
* If an order is rejected by a TEvo Seller, there is a configuration on the API buyer's account for Buy / Sell orders to auto-cancel the customers order or not. If not, the API will allow for a substitute ticket to be created as a new purchase order, associated to the original via the same Orders / Create endpoint.
* The two order links, original and new, will share an order group id.
* Here is a link to a page the shows the calls that could be made to create a substitution purchase order: HOW TO: Process a Substitution via the API
All order types use the same endpoint, and the response to a successful request will be the order that was created.