Disabling american express

Question:
How do I disable Amex in my store?

Product:
Payment method is too expensive and too risky. I want to disable it.

What are you trying to achieve:
I want to save money and avoid chargeback which Amex carholder are reknown for.

What have you already tried:
Help section no article on the topic. it seems to be all or nothing.

Additional information: