My DH and I have the same level and cruise history with NCL, but he got the two coupons and I didn’t.
However, when I try to do a mock booking using his account and a link from the coupon page for eligible cruises, no coupon is showing as available when I get to the payment stage. I tried both 20% and 50% coupons and several cruises.
These are applications, something similar to FaceTime which you could probably use as well, audio only.
My take, based on my experience, is that wi if calling should work, as my audio connection on the ship’s wi fi was fine.