Stop negative card transaction from amex to be view by employee

I would like to stop employees from being able to submit negative card transactions(Payments). The would come in from the amex load , but it should not be viewable to the employees. Is there a role or a configuration that can help. We would not like to touch the interface or use page personalizarion.

Is there some way to restrict it based on merchant details(category code, name etc)

Thanks

Sourav