Credit Free Months with PayPal Express

I've got a customer who is currently paying monthly recurring for their Pro Site. I'd like to extend their site for 2 months for free. However when I extend in network admin it doesn't change any of the payment due dates. Is it possible to extend the site for free for 2 months and notify PayPal to not charge him? Or will the system catch this on the next billing cycle?

I guess my question is: what is the correct way to credit someone free time and not have PayPal charge them for it?