payment gateway for virtual and phisical product

Hello.
I have a book shop, and everything was fine, the payment for the orders were made by card or by cash on delivery.

I now have a new product, an online course, which is a virtual product, and is set to be paid only by card.

Everything works fine, if they order only the course. But if they ad a book in the cart, besides the course, then the cash on delivery becomes available.

I would like a solution, that if there is a virtual product in the cart, to be paid only with card (not c.o.d.)

Thank you.