Can I speed up or cancel a swap transaction?

Unfortunately not. Swap transactions are irreversible.

Trying to cancel or speed up a pending swap transaction (by using RBF or custom nonce) will result in another transaction outside of the swap process. Changelly swap addresses are non-reusable and only one transaction hash can correspond to one Changelly address.

Once a transaction is confirmed on the blockchain, it cannot be rolled back. So, if you are going to exchange cryptocurrency, be sure to double check all payment details carefully before sending.