Woocommerce free shipping based on payment gateway selected

I’m trying to get free shipping available when a certain Payment gateway is selected. So I’ve got 2 payment gateways:

if Payment gateway 1 selected –> With shipping costs
if Payment gateway 2 selected –> No shipping costs (free shipping)

I can’t find how to check which payment gateway selected so that’s my first problem.

Can anyone solve my problem?

Thanks in advance.