Is there any way to stop a pending transaction from processing?
There is not, a pending transaction needs to get posted first and the can be reversed after if funds are to be returned or the transaction can just expire natually.
Additionally, we do not control the lifecycle of a card transaction once approved.Once approved, that is us promising the network that the merchant can take the funds from the bank. If they do, we have to respect it and pursue disputes if the end-customer claims it was fraudulent, or they have to take it up with the merchant. We have no control over how a merchant handles the authorization after the approval.