To redeem your cashback rewards, simply choose Discover on Apple Pay, select "Tap for Details" when you get the redemption message and then tap to redeem your bonus. There's just one important thing to take note of: you can't redeem your rewards if you're on T-Mobile's network. Unfortunately, it could make redemption harder while you're on the go if you're a T-Mo customer, since you'll have to disconnect your mobile internet and find a WiFi connection instead. We were told that the card provider is working to make the feature available to all Apple Pay users, though, so the issue could be fixed in the near future.