There is no way to change or cancel your transaction

Once the transaction is initiated and the swap is created it should not be changed or cancelled. Once the transaction is paid for, it is irrevocable and irreversible. All this is happening on the blockchain and such transactions are final by their very nature.

As long as the transaction has not been paid for, you can just abandon it and create a new one, but your access to Ramp can get restricted if you do that notoriously.