How do I cancel my Apple Pay account? I've had fraud purchases recently.

You are not talking to Apple here or anyone who can access your account - this is a user to user forum.

If you have had fraudulent activity on a card connected to Apple Pay, it’s best to call/contact the card issuer directly to deal with it.

Simply remove the card from you Wallet app. If you need assistance with that post a reply.

You can also follow t.more’s excellent advice and contact Apple Support.